On my ofna 9.5 I had to bevel the edges of the flywheel opening to help the radius of the wheel get up to the flywheel. There wasn't a lower engine mount available. Once you bump you won't want to mess with anything else. I'm not sure how your motor was, but some rear start engines use a fixed pin on the end of the crank to engage the starting gear. The disadvantage of this is a shaft extension flying around in a bronze bushing. There is the potential for air leaks and it robs power. If you have the option once you get the hang of the box you can remove the back plate starter and replace it with a normal back plate. The normal back plate doesn't cover up the rear transfer ports nearly as much so the engine will breath better. On the force brand and force built engines the pin is spring loaded and depresses into the crank. The start plate has a curved ramp with a hole that catches the pin only when you pull it. It makes the engine not have to carry the starter around with it. If your engine has a fixed pin you have to dremil/file/machine the pin flat to put a standard back plate in, and there's no going back unless you buy a new crank.