I got a little wet at one point, but I still made several, freeway test runs of my oil cooler today. My latest fender modification was successful. Riding the same stretch of freeway that yielded a high oil temperature of 279 degrees yesterday, my high oil temperature was 248 degrees today.
I also rode the same section of freeway that yielded a high oil temperature of 255 degrees without my front fender mounted. Today, with my modified fender mounted, I reached a high oil temperature of 253 degrees. Riding back home along this same stretch of freeway, I encountered very strong headwinds that kept my speed at 75 mph while riding wide-open-throttle. My high oil temperature under these conditions was 235 degrees.
This oil cooler installation works very well.

Other than the XR650R C/S sprocket, I think this is the best modification I have made to my XR650L.

I am very pleased with the current configuration of my oil cooler; at this point I don't plan to make any further changes. I will certainly report if I encounter any difficulties with this installation.
Another forum member promised to loan me his XRs Only temperature gauge next week. After riding a few miles with his oil dipstick thermometer, I will report the difference in temperature between my temperature probe located near the engine, and the oil dipstick thermometer located in the oil reservoir.
Spud