A buddy of mine had this same issue with his PA12 on Edos. The IA he had working on the plane was convinced the wings were out of rig and spent all day dorking around with them. I went out and took her for a turn around the patch and played with the water rudders in the air (putting them down then up again) like you, when down she was fine, when up it pulled to the left. 10 minutes with a tape and a straight edge adjusting the turnbuckles on the water rudders and she flys straight as an arrow, then I had to re-rig the wings to get the roll straightened out that the IA had screwed up.
Avid C Heavy Hauler
"I would rather die trying to live, than live trying not to die"