Nikos,

I don't know if they are all built the same but on mine the firewall is square with no right
thrust built in, but if you mount your engine that way the spinner gap will be uneven because
the nose is built to accomodate right thrust. I used a Hyde ARIA mount with the built in nose ring
and offset it slightly to the left of center on the firewall and made a shim to go behind the mount
to angle it slightly for the desired right thrust. I don't know how much it's angled, I just made it fit
even with the spinner back plate.
I used regular locking nuts on a plywood ring behind the firewall for mounting the motor mount.
If I was building another one I would use the Hatori short pipe

tommy s