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I installed a new set of side rails on my Boston Whaler 17 Custom (Eastport interior) that was originally a Super Sport Limited model. I bought the side rail set from Nauset Marine so the set was an OE Boston Whaler part. The stanchions, what you call stand-offs, were the same length. When I installed my rails, I was careful to screw down the base stanchions first at all four points on the surface above the thwart board channel but directly below the wood backing in the interior bulkhead (there are 4 locations). You must be certain to screw the side stanchions where the plywood backing plate is located in the interior bulkhead. I was able to see the outline of the wood located below the gelcoat using a light. I also installed the rails with the T fitting allen heads facing outward, so that the allen heads did not cause injury if you rub up against them. You will be drilling new holes in your boat so use the correct undersized bit.