Nair - Nair's hitbox encompasses Lucas's body as well as a small area just outside of his body in all directions. The hitbox size does not vary on the first 7 hits although the animation makes it look like it would. The hitbox is slightly larger in front of Lucas than it is behind him. The 8th hit of Nair (the knockback hit) extends the hitbox slightly vertical, both below and above Lucas.
This makes Nair effective for juggling as it both can outlast airdodges and has a surprising hitbox change that doesn't show in the animation at the very end of the move. Also, because of the way Lucas's jumps work, you will float at the top of your jump for a moment after the Nair which is a great time to do an Uair if they did manage to airdodge through your Nair.
About that Nair to Utilt combo: it doesn't always work. At low percentages, characters with fast aerials can hit you before you can hit them. Also many characters can jump out of it if they're mashing A. Also, depending on the position of the opponent after the unautocancelled Nair, your Utilt may sourspot them which will not hit them far enough away and they can hit you during your lag after Utilt. Also some characters who fall fast can shield during your lag from Nair and then punish your lag after Utilt. At very low percentages I recommend using jab combos after this instead because it's not escapable with few exceptions and can be jab cancelled to retreat or follow up. At higher percentages Utilt will be more acceptable, however once you cross the 100% mark or possibly even lower, you're much better off to just do a short hop Uair since it kills at lower percentages and will come out fast enough.
Fair - Fair's hitbox lingers a disturbingly long time. Anytime Lucas's foot is held out it can hit someone. Also the electricity hit (sweetspot) remains at the tip of Lucas's foot even after the hexagon from the attack has disappeared. Because of this, you can sometimes get some easy hits off with Fair by simply using it well ahead of time so that the opponent would expect the attack is over when it actually isn't. This tends to make falling Fairs especially useful. The hitbox extends its largest vertically at the very center of the hexagon. This allows Full hop Fairs to hit characters like Mario who are barely tall enough for it to work. The sourspot remains longest by a small margin which is of course Lucas's foot and leg themselves and has very little knockback but extends almost to the middle of Lucas's body. If an opponent is hit by a Fair from the middle of Lucas's body while he is facing the other direction, they will be hit the opposite direction that Lucas is facing. This is also possible with the very edge of the hexagon at the tip of Lucas's foot allowing reverse Fairs similar to that of Captain Falcon's reverse Knee in Melee only not near as sweet and it rarely occurs.
Uair - Uair's hitbox extends a good deal above Lucas's head (where it shines for a second) down to around the middle of his body. Horizontally it extends much further behind him which makes RARing important for this move. Uair's knockback is consistently diagonally upward in the opposite direction that Lucas is facing unless he hits with the front of his forehead in which case it is diagonally upward in the direction he is facing.
Uair is unique in that it will hit any opponent while they are on the ground if you full hop and immediately use it. However, it's irritatingly difficult to do and I need to test more to see if it's worth using as an approach due to the small size of its hitbox.
Dair - Dair's hitbox covers the entirety of Lucas's front except for a small area on his head and also the hexagons below him. The hitbox ends around the center of his body and only extends slightly behind him at the feet.
Just a few things I've been testing out and messing with that I thought I'd share. I'm sure some of it is known since it's pretty obvious but I wanted to see what some of you think on a few things, especially about Nair.
This makes Nair effective for juggling as it both can outlast airdodges and has a surprising hitbox change that doesn't show in the animation at the very end of the move. Also, because of the way Lucas's jumps work, you will float at the top of your jump for a moment after the Nair which is a great time to do an Uair if they did manage to airdodge through your Nair.
About that Nair to Utilt combo: it doesn't always work. At low percentages, characters with fast aerials can hit you before you can hit them. Also many characters can jump out of it if they're mashing A. Also, depending on the position of the opponent after the unautocancelled Nair, your Utilt may sourspot them which will not hit them far enough away and they can hit you during your lag after Utilt. Also some characters who fall fast can shield during your lag from Nair and then punish your lag after Utilt. At very low percentages I recommend using jab combos after this instead because it's not escapable with few exceptions and can be jab cancelled to retreat or follow up. At higher percentages Utilt will be more acceptable, however once you cross the 100% mark or possibly even lower, you're much better off to just do a short hop Uair since it kills at lower percentages and will come out fast enough.
Fair - Fair's hitbox lingers a disturbingly long time. Anytime Lucas's foot is held out it can hit someone. Also the electricity hit (sweetspot) remains at the tip of Lucas's foot even after the hexagon from the attack has disappeared. Because of this, you can sometimes get some easy hits off with Fair by simply using it well ahead of time so that the opponent would expect the attack is over when it actually isn't. This tends to make falling Fairs especially useful. The hitbox extends its largest vertically at the very center of the hexagon. This allows Full hop Fairs to hit characters like Mario who are barely tall enough for it to work. The sourspot remains longest by a small margin which is of course Lucas's foot and leg themselves and has very little knockback but extends almost to the middle of Lucas's body. If an opponent is hit by a Fair from the middle of Lucas's body while he is facing the other direction, they will be hit the opposite direction that Lucas is facing. This is also possible with the very edge of the hexagon at the tip of Lucas's foot allowing reverse Fairs similar to that of Captain Falcon's reverse Knee in Melee only not near as sweet and it rarely occurs.
Uair - Uair's hitbox extends a good deal above Lucas's head (where it shines for a second) down to around the middle of his body. Horizontally it extends much further behind him which makes RARing important for this move. Uair's knockback is consistently diagonally upward in the opposite direction that Lucas is facing unless he hits with the front of his forehead in which case it is diagonally upward in the direction he is facing.
Uair is unique in that it will hit any opponent while they are on the ground if you full hop and immediately use it. However, it's irritatingly difficult to do and I need to test more to see if it's worth using as an approach due to the small size of its hitbox.
Dair - Dair's hitbox covers the entirety of Lucas's front except for a small area on his head and also the hexagons below him. The hitbox ends around the center of his body and only extends slightly behind him at the feet.
Just a few things I've been testing out and messing with that I thought I'd share. I'm sure some of it is known since it's pretty obvious but I wanted to see what some of you think on a few things, especially about Nair.