Wi-Fli definately has a long cage, but most people running wi-fli would probably do so knowingly, for cyclocross or unique drivetrain requirement where you want a 32T rear cassette. I'm not aware of Medium vs Short Red cages, though I see Wiggle sells "Medium" but it's WiFli... to me, WiFli = long. A WiFli backplate definitely isn't compatible with Fibre-Lyte backplates (currently) and I have no idea about the Red22 compatibility.
The older 10sp Red derailleurs have a slightly different cage shape than the AeroGlide version (new 10sp Red). The new red has a subtle squared-off profile and the cage tab on the new Red is attached to the front plate, rather than the back plate with the old Red. At least when I bought my last Fibre-Lyte plate, they were all modeled off the old Red and the standard FL included a cage tab on the backplate (super lite version does not, can be handy though).
Therefore, installing the FL plate on new Red means removing the cage tab. This will also leave a weird carbon piece sticking out that is no longer needed. It'll work fine like this, but it looks more polished if you can file that piece down.
Old Red (no modifications to FL plate)
New Red (with modifications to FL plate)
Sorry to offend with my ride-it-until-it-implodes winter chain and cassette.