Wingspan99 had this same plane, and noticed that the horizontal stab came from SIG out of the box with -2 degrees incidence. Made for some really different and squirrelly handling at the opposite ends of the throttle. It handled the same as your plane did. He built a new stab for it, which seemed to help alot. This plane also has a very small landing envelope, too fast by a couple mph and it would float, a couple mph slower, and it would snap stall. Landings by far were the largest pucker factor of the entire flights on that plane. You can also try to mix in either spoilerons or flaperons to help with landings, after you get the balance, trimming, and incidence set correctly.

Shoot wingspan99 a message about the mods he made on his cap, I'm sure he wouldnt mind giving you the details.

Steve