So I have been fighting this problem all summer long with no success. I have tried everything that has been suggested here and much more. This is really not a hard snap - it's more of a quick barrel role. I have a short video of what is happening, just not sure how to post it. There are two very short clips on the video. The first is of a power-off dive with a hard pull (full up on low rates) it basically barrel roles to the right. No rudder or aileron except at the bottom of the loop to stop the role. The second clip is of level flight at half throttle with the same barrel role. The strange thing is that if I put 5 clicks left rudder, off of trim, it roles the other direction. It is very sensative to rudder. 3 clicks left and it almost stops the role and is close to acceptable (but then the rudder is out of trim). On an inverted push it actually stays flat with rudder trimmed. Any left or right rudder off of trim causes an inverted push to role over one way or the other. My flying buddies have all tried the same maneuvers with their planes (other brands), none of which behaved like this.

Here is what I have checked and tried so far.

Ran through several different trimming sequences. This plane is now very well trimmed.
Moved CG up to 1" up and back with no change to behavior
added weight to wing tips - no change
added trip on wing - no change
Swapped wings, left to right upside down (very confusing) No change
Checked all incedences, all are right on and same left and right
Checked and matched all throws and travel on control surfaces
Changed throws on right-side elevator, plus and minus to left side - no change
Closely inspected the airfoil - All looks very good. it appears that this is a NACA-12 Airfoil. Does anyone have info on what airfoil was used when this plane was designed? I would like to do a closer check on the leading edge curve.
I believe the power off dive with a pull rules out any p-factor, torque or gyro.
There is a slight twist to the airframe, maybe 2deg. I have fixed the horizontal stab to be parrallel with the wings, but the rudder is still slightly off.

I fly this plane either fairly fast or completley stalled. It does a great elevator and harrier starting with a dive and a full high-rate pull. On a gradual pull it tracks perfectly straignt. It's the in-detween that drives me crazy (and gets the heart pumping real fast). It's a handfull landing if it gets too slow. It will always drop the right wing, unless I am very quick with the left rudder (strange as it sounds it will do this regardless of which wing I put on the right side :<o ).

Why is it sooo sensitive to the rudder?
Any other ideas?? I'm running out.