The hard parts already done. You already have a whole right in the center of the guide. The Dremel tool I use has a two half inch cutting wheel. When I'm doing steel I crank that baby is fast as fast as it will go, for me I think that's about 16,000 RPM. Watch out for those tiny red hot flakes of steel they shoot everywhere, so wear the eye gear and make sure it's done in a very well illuminated place.
you only get one chance at it so it's probably a good idea to go over the passes a couple of times before you actually turn the thing on. This way you know you won't have the unexpected bump or pull at the wrong time or place.
I remember doing something very close to that a few years ago and it worked okay for me.
Mike Frye the bike guy
A.K.A. Frye bikes