I did a lot of this to clean the edge of plexi. If you take off very little, an ordinary straight bit works fine, not sure if a spiral may be better.
Offset your fence. Put a straight edge on the offset side. Line the fence up to the bit.
I guess the size limit would be the bit's cutting length as long as you're taking off very little.
The offset in the drawing is very exaggerated. Maybe use playing card spacers if you have adjustable faces on your fence. The adjustment of the fence is critical or you'll get snipe at the end of the cut. Test on a scrap first.
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