I used my 8.5' 8 wt St. Croix. It's fairly soft in the tip so the presentations have been delicate enough not to spook the fish. I suppose that I could go down to my 6 wt, but with my luck I'd latch onto one of the 12 pounders and be fighting it for far too long. I know carp aren't as delicate as trout, but I still like to be able to whip them in a reasonable amount of time so they can recover quickly.
John, your nymph suggestion is good. I've tried some GRHEs and stonefly nymphs, unweighted so that they sink sloooowly. Plenty of interest, but not enough for a take. I have a few ideas that I'll try to play out and keep you posted.
Here's to the Golden Ghost!