Funny you should ask about the Extra. In the February issue of either RCM or MAN there is a very good article that talks about the Extra and its 3-D capability. For example; first there is no such thing as a full scale Extra 330. The Extra 300 got its name from the horsepower of its engine (300 HP). When someone put the 330 hp engine in the newer ones, folks in the RC manufacturing world started calling it the Extra 330, but the real airplane kept the extra 300 name just with the bigger engine option. (It has to do with the FAA certification process, the fact that its a French manufactured airplane and other complications, so the real airplane kept its old name.)

Now for the 3-D stuff. A full scale Extra flyer modified his Extra 300 L to the 300XL (or LX) version based on improvements in the airplane he saw RC'rs incorporate in their TOC airplanes. The X in the Extra 300XL name came from installing bigger flight controls and stabilizers on the original fuselage. The horizontal stab was lowered 8% to fix a trim coupling problem and the full scale guys adopted these changes in their airplanes. The X in the full scale airplanes name stands for eXperimental. Again, the full scale airplane was not re certified with the bigger surfaces on it, so its flown under an experimental airworthiness certificate.

Anyway, if you want a model of an Extra for 3-D flying you should insure it is one of the X type with bigger surfaces and relocated horizontal stabilizer.

Weather the RC manufacturers know about this probably depends on which manufacturer you get your airplane from. So, you have to be careful to ensure they are not just selling an extra 300L as an Extra 330XL just because they like the name.

Of course you know the S in the Extras name stands for single seat and the L stands for duel seats.

I'm just repeating what I read from memory, so don't take it as gospel. The article is very well written and explains this stuff much better than I did.