Sig 4*'s aren't difficult builds at all. With Sigs laser cutting and interlocking construction you'd get as much building experience putting together a 100 piece jigsaw puzzle. I'm not saying the 4*'s are bad planes, on the contrary they are excellent low wing trainers, especially being tail draggers because you'll need that experience for a warbird. The running joke with a lot of Sig planes is "open the box, pour in glue, shake box, pour out airplane". The second kit plane I built was the Great Planes .40 size Corsair and I learned a great deal more with that one. It wasn't difficult per se, but it wasn't as easy as just pouring glue on it like a 4* either. With the GP Corsair I got to try my hand at shaping balsa as well since you have to shape the wingtips and turtle deck from balsa blocks. Fully sheeted fuse (experience sheeting those curved surfaces). Single Aileron servo/bellcrank setup I'd never done before (I'm betting the Giants have a servo per surface tho). About the only thing it doesn't throw at you are the flaps a larger build will have you do. The Great Planes Corsair also happens to be a great flier as luck would have it. Granted it's in no way a scale model, but no one's left wondering what it is either. I built this plane because ultimately I wanted to build warbirds as well. This way I could try my hand at it without jumping off the deep end.