4TEC, It sounds like you know what your doing. Did the plan call for any down thrust in the design. If not adding a degree or two will help with the balooning. With most trainers I've flown the nose actualy dips a touch when you add power due to the downtrust, and conversley the nose rises when you let off the power. I would also check the wing and stab incidence against the plan. Basicly a trainer set up correctly should need 0 elevator for ROG . By the way I just reread your post and now realise you didn't build the plane. I would seriously look at the issues I've noted above and be sure the CG is not too far aft. I'll bet 1,2 or all three are the problem. Perhaps it's a good design and a crappy build.

Rrragman