I have the same problem, man. Her feet are the most ticklish part of her body, but that being the case, she HATES it and won't let me touch them. Not only that, but try doing it without restraints, and I'm liable to get some teeth knocked out. Do it with restraints, and the whole bed will probably collapse from the intense struggling, and I'll have one pissed off girlfriend.
The problem with some of you responding here is that the whole idea doesn't compute to you because you're applying it to your fantasies, where more ticklish = more pleasurable, and not real life where the opposite can be, and often is, true. The truth is that being too ticklish really can make the experience unpleasant, and it really is a legitimate problem.