Finn,

Sorry for the late reply to your 9/7/19 post.

I used a James cowl on my RV 7 A with a Renesis 4 port.   My water  radiator was a Scirocco drag race radiator – core measures  13 in wide x 22 in long and 2.5 inch thick for 715  cubic inches.  For the oil I used a stock RX-7 oil cooler (2.0 inch thick) with the bypass plugged.  The radiators are mounted side by side under the engine motor mount.  The aft end of  the radiator assembly is against the cowl bottom and the radiator assembly is bolted to the motor mount structure at a 30 deg angle with the high end just above the James cowl air  inlet under the spinner.   The air flows in under the radiator assy. up through the rads and out at the firewall.

I cut a small opening above the James cowl  cooling air inlet to use for engine combustion air.  In the cowl under the radiator assembly I built a pinched duct to try to distribute the airflow evenly through the radiators. (Probably could improve it)   If it is real hot when I takeoff I reduce throttle as required to control my oil temp to not exceed 220 F. My water temp is usually 10 deg cooler than the oil temp.  I have taken off fully loaded when the air temp. was 105 deg F. and climbed at 20 inches manifold pressure to control temps. 

I have about 860 hours on the engine.  The doner car had about 9,000 miles on it when it was wrecked.  The engine has never had the rotor assembly taken apart.  Most of my flying now is 10 minute flights from 40XS to GTU to play tennis 3 - 4 times a week.