RCU Forums - Slow stick problems. Help!

I’m asking this question on behalf of my bro-in-law as he hasn’t a computer. He has just built up a GWS slow stick. We have both successfully built up several GWS models so this build up is certainly not beyond his ability. It’s set up with HS-55 servos, a little 280-300 brushed motor and stock gear-box, flying on a 2cell 900mah LiPo battery. With the leading edge of the wing at 5” from the front of the stick, she balances out at 4” back of the leading edge. This seems to be OK according to the instructions in the manual. The problem is, the plane takes off and flies but is constantly porposing, (sp?) up and down and will not trim out to level flight regardless of the power setting. I have a slo-V which doesn’t have this problem. Any suggestions would be greatly appreciated. Thanks.
Rick