KK I'm ready to have some ideas bounced off of me.
Also some good ole Sheik vs Falcon play by le me. I had gone falco the entire tourney but was convinced by a friend that Jace was probably the best practice I would get for a while, so I stuffed some matches in. From the variance in how I do in the matches I feel like I fell back on some old bad habits every now and then and got punished for them pretty hard. At least I get slightly better at chech tasing.
darkatma vs Jace:
http://www.youtube.com/watch?v=cKP9Z8f8tu0
Anyways my problem matchups still seem to be fox falco. It seems at the last 3 nationals I went to I lost to a falco, then a fox every single time
And two of those were the exact same 2 people in the same exact order =[ (Peepee, SFAT combo)
vs Fox, sparingly attempt walling him out, but don't abuse it so you don't lose too much space. Offstage, avoid his shine at all costs and space so you don't get baired out of your air-jump/upb from the ledge. If you're in the zone, predict his movement for punishments. Stuff his movement! Trading with Fox is usually not that bad...and most of the time he's more busy trying to move around than attempting to crouch cancel or summon hitboxes, so focus on stuffing his movement (bair/nair even if they'll sour hit).
You can shieldgrab their dair as it has low shieldstun (unless they consistently time it perfectly which is rare for any player). You can roll out after blocking any aerial by holding the C-stick during shieldstun (or as soon as the aerial touches your shield). You can also shieldgrab their bair if they're in range as the timing for ASAP shine can be tough for them.
vs Falco, get him from an angle above him (have you played Dive Kick? LOL). You can shieldgrab any SHFFL he executes too quickly as it takes him longer to land from his short-hops. Like vs Fox, you can roll out after blocking any aerial before the shine can hit you. If he lasers your shield right next to you, he's probably going to shine. If he's a bit too far away from you to shine you, he'll probably want to dash JC grab you (Falcos LOVE attempting this), so you can predict that and punish with spot-dodge or nair or maybe even shieldgrab them first (or maybe just get away with a roll).
Abuse ledge camping. His shine won't kill you like Fox's (and you'll often need to do it to regenerate your shield unless your decisions are just amazing and you're not even spending much of it).
Against both, it's very important to master dthrow tech chase so you ALWAYS follow up on those (if they keep teching it, it's an infinite until you get them offstage. there's already a thread about it here in the Sheik board). You have to also be at least decent at edgeguarding them (bairs are good, baiting airdodges is good, needle if they start an upb at needle height, dsmash/ftilt their sideb, preemptively jump off to KO with fair/bair if you predict a high upb, etc.).
Remember to bait spot-dodges/shines inbetween the stuff they do. Many spacie players do this as a panic thing.
Sweetspot bair outranges their whole aerial game. Tech chase uair vs platforms works wonders.
That's the most important stuff I know about those match-ups.
The most important piece of advice I can give you is to watch a TON of m2k matches. That's how I'm learning, like, everything.