thinking of mounting a fan to one of the rads on the 300
did u mount it front or back of the radMy 4 stroke Beta boils bit time on the truly tough tech trails. I've even had it boil going down the mountain. If I can get into second gear so there is some air flow it's not an issue. It's those prolonged 1st gear with clutch slippage really slow going sections that make it boil. I added a fan I harvested from an old computer server and it's never boiled since. It might not be water proof like a real bike fan, but it was free and I have several spares.
Like has already been said, if you don't have boiling issues you don't need it.