A job for either a router or a laminate trimmer (AKA - Small Router).
Some folks are crazy enough to use a dremel as a router, and on truly tiny things that might even make sense to me (though I'm no fan of the crummy bearings most of them have), but here it's a router.
The brave might go freehand, the burned-once will use a template/jig/sled to control travel and keep the router on track.
Whether this is a job for you or someone else is pretty much your call. Practice on scrap, and keep track of your fingers, so you have as many when you stop as when you started. Anything (including a dremel) that can cut wood can cut flesh...
You can also go old-school and use a chisel. It's a small amount you are trying to cut. Practice that on scrap too. Make sure the chisel is SHARP.
Yamaha RBX270 (mfd. by kaohsiung Yamaha Ltd, Taiwan) D'Addario EBT92s, Peavey TNT130
Blessing Artist metal pneumatic piccolo fretless bass (that's a trombone, folks ;-)