Jim, IF you really need some how to trim a bipe ideas i have a few items I have kept from old magazines. The IF is there because I would have to find them and put them into a file and email them to you. If you really need them I will mail them to you tonight.
Usually the reason for a sharper pull to the left on take off with a bipe is the P-Factor on a short coupled plane. Bipes like the Tiger Moth aren't effected like some short coupled plane like an AeroMaster or HOG. One old trick used instead of adding a bunch of engine right thrust angle is to have the left aileron set at neutral or centered and then add about 1/16 to 3/32 up in the right aileron to help the adversed Yaw.