Pietro, I just installed the Century Jet retracts in mine last night. I did need to cut out the forward part of the U shaped rail you speak of in addition to a chunk of the spar using the wood mounting blocks supplied with the kit. Remember that the installed retracts are very rigid and will take the place of the lost structure. I did go to Home Depot and get some 1" long screws to make sure the retracts are very well secured. I'm not going to fabricate new gear doors just now, but I think this installation is set deep enough into the wing that some scale gear doors woudl fit nicely (scale gear doors have a hump in the center).

We shall see. More about the final results and discussion about the maiden flight some time tomorrow!

Tom