I think all this comes down to what you are seeing for oil temps after your run. Are you running a filled block? What type of track and sled are you running on, Whats the length (seconds) of your runs?. I know up here we have a mix of clay and sand/ stone dust tracks, so our run times vary by up to 15 seconds. I run a 50W as well with bigger bottom end clearance so I really do not like temps over the 150 mark. Usually I can get two back to back (say test hook and re run) before temps are over 180 at the end of the second pass, put there's no pull off for me if this happens. I have ran an external cooler (it was a huge SS coolant to oil unit off of a motor home) with two filters (one before and after) plumbed right into the engines oiling system. I found however that even though the cooler had very little restriction the extra filtering created by pass issues. I have since went to a complete stand alone system with its own pick up in the pan, pump, cooler and return to pan and run it between runs.