Do I have to record a video with me voicing frame by frame everything?
At 0%, dthrow does not chaingrab, as Fox lands on the ground TOO EARLY for him not to be able to escape it with a spotdodge (he "feels the ground" around frame 43 at 0%).
After TWO FORWARD THROWS, i.e. SOMEWHERE ABOVE 4% (and in this case 7%), FOX WILL LAND ON THE GROUND FRAME 45, WHERE A SPOT DODGE WON'T COME OUT UNTIL FRAME 49.
Marth's down throw has him free frame 34, with an 8 frame dash grab, you have to start grabbing by frame 40. WHY IT STOPS AT 28%, IS BECAUSE AT THE LEVEL OF DECAY DTHROW HAS AFTER 5 THROWS, HE WILL BE ABLE TO AIR DODGE FRAME 26.
IF YOU HAD dthrow decayed more? Maybe you'd need to start cging him a couple of percent later and it would go longer, maybe not.
EXPLAINATION:
Marth's throws have a damage output increasing at yada yada speed per percent damage.
Marth's throws, once they reach a certain damage (it seems semi-dependant on character... or maybe just Fox got screwed over hard) the THROW you use will have it's PHYSICAL PROPERTIES CHANGED.
The start up throws have larger hit stun, and the trajectory an opponent moves is SET (i.e. no DI). YES, DI DOES NOT CHANGE ANYTHING WITH THE THROWS AT THESE PERCENTS.
The 'second' throws have considerably LESS hit stun and can be DI'D.
Hence with the use of decaying throws in certain ways, the "start up" throws can be extended longer, maintaining the awesome frame advantage they have.
e.g. A fresh fthrow will hit it's "second" part on Bowser at 8%, he will be able to start air dodging at frame 32, leaving you stunned until frame 38. If it was to return it's first part bowser wouldn't be able to airdodge until frame 48 (and will most likely land on the ground during this time, incurring further landing lag penalties).
If for some odd reason, you fthrow was completely decayed (9 times), you could fthrow cg Bowser from 0-18%.
So in a real occasion,
fthrow 1: 0-4%
fthrow 2: 4-7%
fthrow 3: 7-11%
Fthrow 4: Isn't a guaranteed cg.