Maybe I have an F 90 from a later run because I can't find any of the problems with the ribs and servo trays also my manual is full of warnings about flutter, there is at least three warnings in seperate spots in the manual. I think I have a couple of Hitec 615 metal gear servo's that I'll use on the ailarons and a 645 on rudder with a 6.v pack but I'll just run 605's on the elevators. To me this is a $200.00 dollar box of fun so I'm not getting carried away with using digitals and I might be the first guy to try an O.S. 1.60 on his fun fun FUN-tana.