RE: super skybolt build
Gary, Go back and look at the fuselage sides as they sit on the plans. Looks like F2 might need some trimming to get the cockpit floor to fit. First thing though, are both sides sitting right on the plans? Check to make sure you don't have glue filling slots for F2, then pull out F2 and look at tab and slot fit. Also trim off any splinters.
Two things I can think of for your engine.
1. Do you need any spacers in front of the firewall? If so, use a piece of standard 1/2 inch plywood from your local home center as part of your spacer. change the bolt pattern from it to your firewall. Then use blindnuts to match it up to your mount.
2. If you need no spacers, Place the mount where it is suppose to be on the firewall. Take a pencil and draw the circle on the inside of the mount. Rotate the mount till you can get blindnuts to clear the cabane slots.