I have built and flown several SPAD designs and I had a similar problem with a FX-Bandit. I had it set up with the ailerons slightly drooped a couple of degrees down. Kind of liking flying with a few degrees of down flaps. At high speeds it would climb like crazy but at landing speeds I had to hold a lot of up elevator. All this changed when I set the ailerons at a couple of degrees up and the problem got better and vanished at about +5 degrees. Might give it a try.