I built two of these. The first basically to plan and the second with a 36" no dihedral wing with spruce spars and ailerons. The three channel flew on an .049 big mig but was switched to a .061. It sits in the hangar most of the time now but has over 15 air hours on her. The four channel is a blast to fly. With a .061 it knife edges across the field performs indefinite inverted flight and outside loops easily.
I've built Herr's Starcruiser (2) Cubs (2) Pitts and P51. My son built their AT6 when he was 14. We have had zero problems with their kits. Are you sure that you got the right front and right rear fuse side together and the left front and rear fuse side together?