It's looking good, how are you going to go about turning it on/off and changing settings?
I'm thinking a short (2"?) piece of PVC pipe with threads on one end, and 2 caps, one with threads, and one without. Cut the center out of the cap without threads out, so you can then stretch a piece of rubber like the finger of a dishwashing glove over the end of the pipe, then cap it with the cap with center cut out. Then cut a hole in the box above where the buttons will be, and marine epoxy in the piece of pvc pipe at the halfway point with the threaded end and screw on cap outside the box, and the hollow cap with rubber dishwashing glove finger on the inside. Then to adjust settings, you can screw off the cap, stick you finger in the pvc pipe and dishwashing glove finger, and push the buttons, all while staying waterproof.
That makes a lot more sense in my head...
I'm doing the same type of thing with the Sov XS, except instead am dealing with rotary switches/pots, so will use the pvc with cap on outside, but with an extended pot shaft, and sealed rotary shaft bushing to keep it watertight with the cap off.