Vented hoods and especially ones with proper ducting going from the back side of the radiator to the top of the hood/vent have a significant effect on the cooling efficiency of a radiator. Thus, you can't properly compare 9Door's PWR (assuming with a non vented hood) radiator's performance to your/Jim's Masiv radiator or say that it's "better" because its possible that the PWR still may be even better at cooling with the same ducting.
IIRC, the more fins per inch makes for a more efficient radiator, but the denser the fins, the quicker they plug up. As you mentioned, the thick Ron Davis has a greater capacity and it takes longer to get to equilibrium but if the Masiv has a better fin design and reaches a lower equilibrium sooner, its thinner core and lighter weight make for a much better combination.
Jim is a great guy and i'm glad you're testing the rad with a fast guy in a demanding environment. If you're radiator is as good or better for less than a RD then it's a no-brainer and a great product for the market. However i'm not sure it's fair to make claims about PWR when the test conditions were so different. They do make the best radiators on the planet and i'm not sure the spec of 9door's radiator but they can be ordered in any thickness, fin count, size, shape, etc... but you get what you pay for and they're a top level motorsport product and are priced accordingly. Keep up the good work testing and developing the Masiv! Do they come with non-painted fins?
Jim - Fan shrouding behind the radiator is good for the fan's cooling ability at low speeds but become a significant restriction at speeds above ~45mph. Mounting fan(s) directly to the radiator is often a good compromise for cooling at speed and in the pits. Also the more air-tight you can make the ducting from the front bumper to the radiator, then from the radiator to the hood, you'll see even larger gains in cooling efficiency than just having a vented hood alone.
Why not run an oil-air heat exchanger on the rear of your car rather than the laminova oil-water?
