John, I've herd that the WM Zero lands fast, but have never seen it first hand. As was illuded to in an earlier post the wings may be glued at the center section increctly. If you have an incidence meter, or know someone with one check the tips. Regardless of washout both wing tips mesured in the same place should have = incidence. Its my bet you will find a higher angle of attack on the left panel.
If so, cut the wing in half and re-epoxy it streight. Once happy with it peal back the covering on either side of the center section and glass it. I'm assuming the wing is Balsa sheeted

If you have strip ailerons adding about 5-10 degrees of spoileron will in effect increase the washout. But the amount it adds is so minimal and dependent on the stiffness of the aileron I dought it will do anything to help the problem.

Good luck