So for FBL units you want your mechanical set up as close as you can to dead on. Dead on is impossible so dont try. In most cases you can get really close which will be good enough. The FBL will handle a lot of the drift for you so no need to worry about the trims. The trims will confuse the FBL unit and cause a huge headache for you.
I dont remember how to do things in the AR series line up. Their should be some kind of setting that will allow you to dial out drift. I know you can level the swash in that unit. A level swash will stop most or close to all drifts. Then after a few flights you can tweek your swash settings to near perfect hands off hovering. It will take a good number of flights to get it set the wag you want it.