You definitely want the water heat. Haven't really heard the cons of summer use but it would seem that you would want it on then also.

I have an offy dual setup with water heat and I ran long tubes from thermostat all the way under the motor to the manifold then from manifold under the motor back to the heater. It seems to work fine and looks clean.

I have heard there is a thermostat housing that has an outlet on the carb side? Using that with stainless hard lines would be the ultimate setup.