CS using if you like, the 4-40 bolts is a reasonable alternative and there is no need to go to inverted bolts. The 4-40's will work fine.

Another alternative that is completely reasonable and reliable in the real world although its dangerous to admit to it, in these forums and that is a #6 sheet metal screw for that displacement. That of course is if you are using a plastic composite engine mount. Works very well indeed if the proper sized pilot holes are drilled. In fact one of the major engine mount manufacturers 'Dave Browns' all include the proper sized sheet metal screws for the size mount and includes the proper size info for the pilot hole.

And CS as far as marking the holes accurately consider the Great Planes hole locater its cheap, and accurate (one of those you can,t live without tools)

John