The pictures help...a lot.

Although the installation appears rigidly mounted, in this case it's not. It's a bit worse than using long one piece standoffs since you have room at several places for the standoff to permit the bolt inside to move a little. Long single piece satndoffs are not a lot better since they permit twisting from engine torque to transfer through the fire wall.

If it was mine and I needed to use a long engine offset then I would use two 3/4" wide hardward blocks the correct length, drilled for the bolts, to attach the engine to the firewall and eliminate the twisting forces.

Pe,

I'm with you when it comes to running the engine the first time on the ground to get everything set, but after that I'm part of the break in while flying crowd.