Yeah, I just mean on the bottom of the hull on the outside. Where it will actually be contacting the water. Any air in the mat could get water behind it and start to delaminate because of all the water rushing underneath the ski. I don't know that for sure it will happen, but it is possible.
Also, your idea for the cooling line is really creative and it looks nice. But before you make it permanent, consider that could be possible for debris to get trapped in those tight bends on the line. There is no reason you cant run that line straight through the bulkhead, then run a hose across the midshaft to your exhaust manifold.
P.S. When talking boats, the port side is the "driver side" and the starboard side is the "passenger side" I always remember this because the word port is 4 letters and so is the word left. So I don't get them confused haha