I measured the pressures in the cowl area. It turns out that the area exiting to the prop disk is acutally not a low pressure area. It is at least 9" H2O above static. This is propably mostly coming from the center portion where the prop has no pitch. I think adding a spinner will block the back flow from this area. The outter portions near the exhaust should be lower.
In the process of measuring the cowl pressures, I measured the pressure in the upper surface of the cowl. Here I got a static pressure of 3" H20 or less relative to Pitot static. So I cut a hole there for the oil cooler exit
I had previously installed a P-51 style scoop on the lower cowl. I measured the pressure differential between this and the exit area on th etop of the cowl and got 12.1" H2O at 160 Kias. The Pitot total pressure at that speed is 15.7" so I think it has good pressure recovery.
Flt Hour 82 Oct 2005
Well I've decided to try and keep this story more up to date. Since it looks like the education is going to continue for a while.

Since the above mods about a month ago I've only made 2 flights and only gotten only real data point. The data indicated that the oil cooling system is working as good as any data so far but not markedly better. The trouble is there is considerable scatter in the data. This data point is on the bottom of the band but without more correlation I can not be sure how much improvement I have. The reason the data is limmitted is because on the first flight after teh Mods and that one data point the engine began running rough. Naturally I returned to base to check it out. After landing I found that the exhaust pipe on the left side was cracked almost in two. That did not cause the rough running. So I had the exhaust welded and I designed and installed a sheet metal brace to hold the pipes. These is not so much as a structural support but mostly to stiffen the system so that it does not resonate at engine RPM. I made another test flight after that but the engine began missing again. I never stabilized on a test point but the temps seemed pretty hot. Perhaps the support I put in is impeding the flow of the radiator cooling air out the rear of the cowl. I'm pretty sure the missing was being caused by a bad "igniter". This is a high current group of tranistor switches that supplies firing current to the coils at the spark plugs. After I changed this I stopped getting the intermittant missing and corresponding drop in the #5 EGT. However, then the #5 EGT climbed as expected up to full EGT while the #6 rose in unision with the #5 up to about 1620 and stopped (around 3800 RPM). This is about the time that the O2 sensor error comes on. So I'm thinking that now that I'm using auto fuel, that I really do need working O2 sensors. The bad sensor made no difference with Av Gas. So a new sensor is going in today and I will see if A) the engine runs smooth, and B) if the temps are any better.