I had tried routing a fancy control box from a single block of wood, but I really couldn't get satisfactory results. I ended up using the box I made according to the plans, made of many little pieces of plywood.
Filleted & glassed to the underside of the deck. I turned the boat upside down to do this, and made an amazingly silly mistake:forgot that left is right/vice versa when upside down, and installed it on the left side! I was concerned about not interfering with the knee braces, and put it rather far forward. I hope that I can reach it.
Had a little trouble finding where to drill into the cavity, and nicked the box a little. Repaired it with dookie fill, and routed out the hole. Doesn't look bad.