Seriously, how much work would need to be put into making a hole bigger in a thick metal plate, and what kind of tools/bits would I need? I kind of need to decide if it's worth the effort so I can respond to the guy. Starting to doubt directly mounting to the plinth is a good idea, since the vibrations due to the idler drive wouldn't be completely rid of by the steel plate anymore. Apparently it would also be a good idea to replace the ball bearing and maybe even the idler wheel so this would be a semi-major project.