1. Cut a balsa shim, and Hot Stuff it to the nose ring of the fuselage. Here I am using an otherwise useless piece of heavy C grain 1/16 balsa.

2. Slip the engine into the bay. Bolt up the backplate, and tack Hot Stuff the spinner back plate to the balsa spacer.

3. Now you can accurately mark/drill the engine mount holes. Shave off the balsa shim from the fuselage nose ring. Congratulations, you now have and accurate, neatly spaced spinner gap.

4. You are "old school", or just "old" if you still call CA glue "Hot Stuff".