Just remeber, there are those that have electric downriggers and those that wish they did! \:D I would also consider making a downrigger mounting board. I have seen these on boats that were obviously set up more for cruising or skiing and part time fishing. It consists of a 2x6 or 2x8 that is attached to the stern of the boat using clamps or by bolting it to the sides. The downrigger mounts are then bolted to the board. It makes it possible remove your downrigger mounts when doing other water activities. Cabelas used to sell a metal downrigger mounting station, you might want to take a look to get some ideas.
As far as telling the wife they are for something other than fishing, procede at your own risk!
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bawddawg, no biscuit!