Hey Spud, great to see you've installed an oil cooler! I haven't been on adv for a few weeks due to time restrictions so I just wanted to leave you some info based on my testing of the 4x6 cooler in the same spot during my USA trip. Also, I'd like to compare it to the relocation to above the skidplate.
Will the tire bottom out on the cooler?
For me it did. My cooler location may have been slightly lower than yours since it is a 4x6.
This only happened once, and it nearly sent me over the handlebars since I hit a pothole very hard. No damage to anything really, just what you see below. (What you can't see is the cooler has a curve to it where the wheel bent it inwards)
Otherwise, with the fender spaced down, the tire would contact the fender often and eventually ripped the screen off the fender. I do have a hard riding style though.
Efficiency of cooling in that location?
Great. Rarely saw above 260F in every situation encountered in 20k miles of riding around the US.
Definitely better than the current location above the skidplate. My theory is that it's too close to the engine and acts like a heatsink. I doubt there is much airflow between the engine and the cooler with how I have it placed.
I've hit 300F at technical riding on Steel Pass in Death Valley.
Slotted vs Drilled for cooling?
I feel that drilling the fender, even with large holes, creates too much turbulence and doesn't allow air to cleanly get to the cooler. It seem Spud has proven this with his recently trials.
Slotting takes longer, but the right way is rarely the easy way.
Mud on the oil cooler inhibiting cooling?
Of course. If you notice higher temps, rinse off the mud and go on your way.
For more info on the 2 cooler locations, visit my thread: http://www.advrider.com/forums/showthread.php?t=689875