Are you just wan ting a water resistant otter box houseing with your controls inside or Do you plan on just hun ting beaches like freshw ater swimming holes up to your neck? If thats the case I'd go with the headphone design and install your controls inside a set of headphones Like greyghosts or similar. Very much like the detectorpro but obviously with your silver umax.
What I did with my compadre units is used a Phyle metal detector . the phmd with the same type controls as the detectorpro pirate pro. and kept the controls inplace and unsoldered them from circuit board. I then reinsterted the compadre into place and gave it a sensitivity ,volume and disc mod. Works like a champ and parted with a few as well. easy way to hunt water with out all the extra hassle and chance of messing up your unit.