Personally, I don’t know how the fizzle it works. I know it first started from X-Men vs Street Fighter. Plus, I’m not good at explaining how it works.
You should hit up Mike_Z or the underground beast Magnetro =] Magnetro explained how it worked along time ago in a nice long post, but I wouldin’t blame him or Mike_Z for not wanting to re-post how it works.
P.S: it’s not called flying screen inf, it’s called purple-gay-rainbows-inf. =P
FSD in XvSF is different with FSD in MvC2. in XvSF you need to hit em a few frames before they recover to execute FSD, while in MvC you just need to trip em while juggling to perferom FSD. For example, FSD in XvSF:
Ryu: on corner c.HP/\sj.LP,sj.LK,sj.MK,sj.HK(FS)/c.LK(OTG),c.MP->c.HP(FSD)
as you can see, FSD is done with c.HP, just right before the opponent recovers from the c.MP. At first the timing is very difficult. Just like “Just Frames” in Tekken. While in MvC2, as i said, “trip” the opponent during a juggle then OTG then launch. That’s it.