You have too muuch DOWN thrust in the engine. While carrying power, the engine dominates the elevator/stab. As soon as you cut the power the elevator will dominate. You said when you do the full power trimmed level flight and cut to idle test that the plane climbs.......right? The plane should start to descend almost immediately. The fix is to put some up thrust in the engine. The up thrust will then have you carry the elevators slighty more down in level flight. Then they will be slightly more down in your POVD, (power off vertical downline) helping to correct the pull to the canopy. Most IMAC style planes need some up thrust in the engine. I build all of my IMAC birds with 1 deg up in the engine.

Now you will probably never get the plane to track a perfect up line and a perfect POVD. You can move the CG back, and this will able you to carry more down elevator to continue to fix the down lines, but at the expense of the plane pulling to the belly in the up lines, and pulling to the belly harder in knife edge.

Set the cg first by flying and trimming the plane in up right straight and level flight and then roll the plane inverted. You should have to hold just a touch of down elevator while inverted. After the CG is set then move to the engine cut test and adjust your up/down thrust. After the CG and the thrust line is set then move to trimming the POVD. The plane will still pull to the canopy slightly. Just mix some down elevator with idle throttle and the problem will be fixed. Now you might be asking yourself about the vertical upline. If it is not straight try adjusting the ailerons. Both up or down. If the plane pulls to the canopy while on an upline, adjust both ailerons up some, and vise versa. This will affect the trim on your POVD. Just adjust the amount of mix as neccesary.

Hope this helps,
Bryan