For future reference for others, it's a lot easier if you take the time to cut the channels flush with the hull using a flexible sawzall blade on the sawzall at the time of cutting away the top portion of the stringer. I know everyone worries alot about cutting a hole in their hull. While it is a worthy effort to try to avoid this, it is NOT a big deal and it quite and easy repair, and in the long run nothing to worry about. We have seen 5 ft slits cut with circular saws cut that were repaired with 10 mins of work and 5 bucks worth of materials. Don't let this deter you from getting things cut out of your boat. This also cuts way down on the amount of grinding required later on. Cutting is much easier and faster than grinding. Having a flat hull surface to work with would allow you to have the option of using a circular saw and setting the blade to a shallow depth and then setting a guide board on the hull to ensure a straight cut along the channel to ensure you would not cut into the sides of the channel. Cutting multiple kerfs into the wood makes it very easy to then chisel it out of the channel. This also works well when removing the transom. Cutting kerfs into the wood at a depth just shy of the outer skin glass will allow you to chisel off the wood very easily. There are various videos, here on the forum demonstrationg these techniques.
