I thought about the keel cooler thing but didn't want those holes in the hull. I did some quick checking, and the k-value or thermal conductivity of GRP is about 1/2 that of water, which really isn't that bad (and a long way from being an insulator). The hull of the boat is in intimate contact with an enormous heat sink. It CAN be done (and there are high heat transfer epoxy resins out there (ie. TIGA R-915, K=1.46, H2O=.5 ). The issue is how big of a heat diffuser you would need to sufficiently conduct away the heat. You could build a diffusing grid on the inside of the boat using the above epoxy and glass.
The temp of the cooling water is below the boiling temp of water, waaay below any ignition temperature.
As for the amazing sail we had, it was only Sidney to Victoria, which is about 5 hrs. You couldn't ask for a better sail, and it was so good to pull into the harbor as well, seeing the lights of downtown reflected in the water.