I am removing the center seat of my Mad River Eclipse And Installing a yoke. Is there some sort of a mathematical formula that is used, or is it just hoist it up and see what feels best for the placement. I have nice wood gunnels so I Don't want to screw up and add more slots. Thanks

buy a clamp on yoke

Put a pole across two sawhorses. Then the canoe on the pole. Then get it to balance (think teeter-totter). Mark the gunnels where they touch the poles. That is your balance point. Now I usually place the yoke a bit ahead of that point so that the canoe's bow starts to lift on its own. When portaging, the weight of your hands will bring it back down if you like, or you can let it lift slightly so you can see where you're going.