Need help installing Recoil pad

[Bullard4075]

I have a new recoil pad (Limbsaver 10003) for my Win94 44 mag Trapper.
This pad is "Precision-Fit" to just screw on.
The previous owner shortened the stock so this no longer fits.
I need to take off a tiny amount all around for a "flush" fit.
I have (borrowed) a table top belt sander. This sander also has a 6" disk sander also.
I tried to just touch the side of the pad to begin to take it down and was not pleased with the feathered appearance
of the rubber part of the side of the pad.
I have stopped to ask advice (unusual for me) before I tear it up.
The pad has a hard plate (bakelite ?) that is slightly smaller than the rest of the pad.
Should I just sand down the plate (we are talking 50 thousands here) and call it good.
If I do need to sand down the rubber how is it done?
I have seen it done in magazines and think I know the basic procedure - taping etc. but don't know
what grit sandpaper should I be using? The sander speed is fixed.
In this case I have installed the pad and with an sharp X-Acto knife scribed around the stock so I
can sand down the pad off of the stock.
I really would like to know the proper way as I have two maybe three other rifles I am
considering for new recoil pads before I return this sander.

[Tycer]

I use 120 on the belt sander. No disc. I lube the belt with WD40. I had one that would feather more than others and I put it in the freezer before the final sand and I used 180 grit on a flat surface to smooth it out.

[marlinman93]

I usually put masking tape on the wood adjacent to the buttplate, then masking tape on the bottom of the pad where it meets the stock. Then mount the pad on the stock and use a felt pen to mark the outline of the stock on the tape. Now you can remove the pad and sand it with the belt (not the disc) until the line is just removed. Sand lengthwise on the pad, not across the thickness of the pad. This will keep the pad from chattering or jumping as you sand.
When you're done, check the fit, and touch up the areas that might be high. I final sand by hand to eliminate any feathers of rubber, with 120 grit.-Vall