I'm using "Well nuts" to dampen the vibration and have discarded the two piece mount that came with the 4star. and am using a one piece instead since I cant use the same blind nuts i need to re-drill new holes... since its an ARF i'm going to assume what downward thrust and all has been built into the Fuse and firewall
So I need to decide just where to place the mount on the fire wall I thought there was instruction on this but alas I cant find it can anyone Help me ...

I think you're doing a bit of over-engineering unless your using a Quadra 35.
The factory firewall angle should be correct where you only need to add slight right thrust on the engine.

Reset your original mount on the firewall and find the center point, or thrust line, from the original. Then center your new mounts in the same place.

Down and right thrust are built into the firewall.
Dennis-

I agree. Sometimes I use thin strips of rubber (Cut from an inner tube) between the mount and the firewall, but for an engine of that size, that's more than enough

I built my 4*40 from a kit. When I put in the firewal, it rested against some wood on the fuse to make an easy fit, yet there is no downthrust. It was my first kit, and it was built like crap, but i'd just do a quick double check on the ARF version

there must be a formula out there that will calculate the center line..thanks any way

got ya , after building a few i'm starting to double check the makers work...and wanted to find out just how you calculate for the center line

strips will not work since the vibration bypasses the rubber strips down the length of the screw into the blind nut and back into the firewall ... great planes sells one and there are a few mounts out there that try to as well but they add weight, well nuts do the same and reduce weight at the same time

Measure down from the top of the firewall...not the top sheating...1"29/32 and the side to side is in the center of the firewall. as mesured off the 4star 60 plans.