It's easy to check out your theory which sounds right on, just shim up the trailing edge of the wing about 1/8 inch something like a scrap piece of plywood and see what kind of elevator trim is then required. Almost as easy would be to reset both ailerons so their neutral point is up 1/8 inch or so. There are a huge number of variables in the construction and setup of any plane such as wing incidence, horizontal tail incidence, control surface rigging, etc. During a repair/rebuild any one and even several of these variables can wind up changed from your original configuration and require you to retrim your airplane. The two items suggested should get you started in the right direction.

Steve Woodruff