As a non intrusive mod I have fitted one of these push on heat-sinks onto the oil filter, and clamped it with a big jubilee clip so it doesn't fall off. I had to carve a small section off it so it fit the x wedge , nothing serious.

http://www.ebay.co.uk/itm/HARLEY-OIL-COO...=item33a39abda7

I am currently fiddling with a stick on thermocouple / readout onto the oil tank to do an A / B test to check effective it is , and keep an eye on oil temp in general. I am concerned about oil temp when I rag it.