Ok I share the same situation (Heavy wing and dont want to do the trim tab).
I started looking real close at both wings to try to find the cause of the heavy wing.
If I looked real close at the wing tips I could see a very slight "dip" in the top rear section of the heavy wing tip. You can see it in this pic.
The other wind did not have this dip.
I decided to try getting the dip out and while I was at it maybe rais this area a little to create a little more lift on the heavy wing by carving some 2" foam into a wedge to make a stiffining rib inside the wingtip.
The problem that I ran into was by doing this the tip skin wanted to wrinkle when I raised it with the rib but I went ahead and epoxied the rib in place and while I was installing it I would guess that I saw it raise this area 1/4" or so.
The tip now lookes like this.
I test flew it and with everything equal. (Both tanks full) It is now only slightly right wing heavy. I would guess that I equelized aprox 1/2 of the imbalance
The result is, It is now close enough that If I start burning fuel from the right tank it will balance within 45min or so. I will leave it like this for a while to see if this will work for my likeing.