It probably is. My calculations were not right, I went 30% MAC as suggested and it was tail heavy, more than likely it is more 25-27% MAC for this plane as the bottom wing staggered forward, and I didn't increased the horizontal stab size to compensate. The overall goal was to be able to fly it as either a regular Cub, or a Stagger Wing Biper Cub. Right now I have too many projects going so I want to get it flying as a Cub for now, and when I have bench space, rip open the lower wings and replace the busted out parts and try again. The most difficult part is building the wing braces that secure the two wings together. The first ones took me a few weeks to get them right.