Have you tried to contact hobby services ?... they are very helpful and will assist you if they can. I have 2 GP cub arf's and I have a OS 70 fs in one, At first I had some problems with the plane trying to right turn as soon as power was applied even with full left rudder I checked the wing incidence and the alignment again everything was straight I also checked the engine's angle of thrust I did notice that there was some right thrust but I don't remember how much.( It's was 2 year's ago )..After flying the plane a few times I noticed that when the engine @ the top of the compression stroke the prop was at about 12 o'clock so when the engine fired the weight of the prop tip was at 9-10 o'clock position I changed the position of the prop 90 deg clockwise and the plane tracks straight without any right tracking. I did'nt like the plane at first now it is one of my favorite's . It is on ski's now and will be on float's this summer...The la 65 you are going to use will be sweet and I think you will like the plane ...good luck and have fun ...JW