Future fins installation

How much wider and deeper then the boxes do I need to cut my slots with the router for future fins? I am thinking 1/8 or 1/16. I searched the archives. The questions has been asked, but I could not find the answer.

Please don’t tell me to buy the kit.

how much deeper is 1/ 32 i think…below the foam…as far as wider that jig you got with set up should do that trick…you set it up then the router does the rest…