Advo,
Was most definitely 3 x 2250L tanks fitted, as I carried out the Leak and Flow checks!
As I said though, this was on the OEU, so was likely connected to trials work, and not something you'd see on a day to day basis. We regularly flew with a 3 x 1500L fit when trailling out to the USA, so it was fairly unique to see a 3 x 2250L fit.
You are quite correct though, ground clearance is incredibly tight, and throughout the RAPTOR trials, with the modified 2250L tank fitted to the shoulder, the aircraft was only ever flown with 1500L tanks fitted, and many times with internals only.
Flipflopman