Or you use a short bit in a normal drill to do one, then use the backing plate as a template to do the others
All of our 18" bits at FM are either dull or bent, so we don't bother using them anymore. Hint, when using this trick, drill to the outside edge of any slotted holes.
Tips on the interior panel cutting: Do it when you're fresh, not when you're tired from a long day of roll bar installation. Cut less than you should, it's much easier to take material away than to add it back in. And with the Sport and Hard Top bars, start by chopping the trim panel right in half
Then, after all that, realize that the bottom of the side panels aren't that visible, so screwups just won't be noticed. The carpet, on the other hand...