I don't think I trimmed mine much because I needed the length for placing the rudder pedal as far aft as possible, I just cut out the lightening holes.
If I had trimmed it, it would have been on my band saw. I can cut .040 easily if I have a reasonably new metal cutting blade. The stock wood cutting blade is useless, but blades are pretty cheap and make a huge difference. It works well enough to cut the thick 3/4" bar stock that's to make the canopy wedge spacer.
The Dremel cut off wheel is a great tool though, I've used it lots. I've got through a lot of sandpaper pieces for the drum attachment, very handy in some of the awkwardly placed and sized openings.
RV-9A #91081, C-GCPT
Dynon SkyView HDX, IO-320 and WW 200RV C/S. Flying as of August 6, 2018