i'm not a real fan of having the oil cooler infront of the radiator (even though thats where they are on our R33's), but unless you get a thick core, you can't get a decent size core to fit in a inner guard.
Duncan, I wouldn't worry about knocking one off in the inner guard. My GTR runs a trust one in the left inner guard, and i went through a fence into a paddock LHS first, and didn' knock it off.
I'll have to check to see how thick the earls one is, I thought it was in the 30mm range
I'll have to get damo to post some pics up of what we did to kerry's gtst, we moved the oil cooler to the inner guard, and ducked it all up