As long as the club doesn't have a policy about barrel lengths shorter than 26"(and many do), no you are not cheating - but as Zippy said you are handicapping yourself with that full choke (and IMO that short barrel). Skeet is all about swing on the target - short barrels tend to start fast and then STOP just as fast - at the wrong time. If you start to get into this more and more, you'll want to pickup a 28" barrel with the Remchokes.
THEN - when you are really feeling froggy and brave, you'll slide over to the 5-stand. After that it is only a matter of time before you come over to the dark side - sporting clays.......