DeWayne could not have said this better!!! I build one awhile back and added depth to the box to allow for foot room...what a mistake! Once completed, the apron of the boat was @ 1" above the surface of the water which caused a major slap with any wave and the boad was nowcompletely unstable. I had to cut @ 4" off of the box to get it back to the original specifications, sold the boat, and bought a MLB.
Just narrow it up so you don't change the displacement. Otherwise you'll have to add ballast or the slap from the foot end will drive you crazy!
I have made one as well, foot drop included. size 13 boots, it is a must. with your legs splayed wide, it really starts to wear on a guy. I personally think the MLB boats are even worse. The supermags are better, but the classic is the worst. After I made mine, I too noticed the slap. But, being a bigger guy, if I get down in mine and put my gear bag up between my legs, for me the slap goes away. Stability was NEVER an issue, I don't know what happened for Dan. Now a few of my buddies who tried my boat who are all smaller than me, they have the slap, one guy just shoved a 15# anchor up by the feet and never had an issue. One buddy went to make one and instead of dropping the box, he raised the foot hump on the top, giving the clearance needed. IF i would make another, this is what I would do. IF I was modifying what I already own, I would narrow up the box about 3" per side, you will still have more than plenty of foot room in my opinion. there was a layout boat made in Appleton years ago, Muddy Bottoms or Muddy Rivers, anyway, Muddy something, they basically looked like a Bankes layout but on the bottom, they went deep in the foot, but narrow, as in your 2 feet were tight together, but upright, not splayed. I sat in one on dry land, was surprisingly comfortable. Never floated one. Anyway, that is my opinon. Best of luck. Love mine, just don't need as many as I have....