Steven.
The long bow is about the easiest to reduce for me.
3 to 5 pounds is pretty easy.
I'd suggest removing a small amount from the belly side with a file or light rasp. You'd be trapping, that is leave the back at full width and maybe a 1/32 from the belly on each side equally from the four edges. Then sand smooth and check weight.
Move slowly and use a block and long strokes when sanding to keep straight lines.
It may take as much as 1/16 inch to get 5 pounds but do it in steps.
Ron