The fins act as a heatsink, a radiator that is being discussed must be liquid filled. if you had a liquid cooled engine it would run very cool, but you would need a water pump. I think you could probally pick one up, and as far as liquid cooling the engine, you would have to modify the head to allow water to run through it, or make one to hold water, but i also agree to have full effect of liquid cooling you would want to have a fan. I would think with this setup you could run as lean as you want, and maybe even go up to a higher fuel. as far as your head being .001 smaller, this is a lot when you look at the fits, remember these engines are ringless, so you cant really play with the clearances. if you are looking to get more power then keep the same clearances, and make a oversized piston, and sleeve, I would think you would see a large diference with about .05 oversized. also if you do this you may want to see if you can get a hone to finish the bore with. the tool marks will also effect the performance, even if you pollish the hell out of it you will still have tool marks