Darock, the trim tab was added to the upper left wing curled upward to provide left trim to counteract the right turn built into the upper wing. The lower wing has strip ailerons and adding a trim tab to the lower wing may cause flutter problems with the ailerons. I’ll leave that experiment for you.

Your comment that, “when the airplane is not in ground effect, the trim tab should be “overpowering””, indicates that you do not understand what I am saying.

I will try to post some pictures of the plane and the trim tab arrangement. The weather here has turned bad again so flying is halted for at least a week.

Oldbob