On my GeeBee-Z, the wall onto which the engine mounts will be installed is not parallel with the wings, i.e. the left side of the firewall is slightly more foreward than the right side of the firewall. This would cause the engine shaft to be pointed to the right. What's the best way to bet the engine shaft pointing dead ahead center?

AND....is there some kind of device I can use to test how well-centered the shaft is?

Is this the KYOSHO one ? If it is I am sure it tells about thrust! I just threw book out on the one I put together

It is supposed to be like that! It will give you right thrust, which will counteract the effect of your engine's torque. Most ARF's and kits have it.

I just wrote up one of these on Vintage & Antique thread ,may help you some. >>>>>>>>>big max 1935