I'd go for 2 tube bars, in my estimation, it's the top one which wears dramatically and the second which gets stupidly hot. I'd be inclined to run a bigger second bar. (What do the yanks do again?-have a look at the storrick website). On a 4 bar rack, bigger bars are likely to run faster!!!!
Also, I'm going to get quotes on importing a pmi chest roller and harness. 2?