What type of wood is it? It looks like some type of softwood. How wide is your router bit? What is the problem you are having while routering/planing? I will be attempting this very soon on my workbench top, and would like to know more. Can you give as many details as possible? For the bottom of my bench i used an electric planer first to trim down the high boards, then switched to a #7 hand plane. It was only the underside so it wasn’t perfect but worked well.

CHRIS, Charlottetown PEI Canada. Anytime you can repurpose, reuse, or recycle, everyone wins!