watchnerd,
Yes, some people have done this with success, but it is not for the faint of heart! The tricky part is that while most of the time a card will report the highest balance ever on the card as the High Balance, on occasion they will report the highest balance they would have reported anyway (as a statement balance).
The way I see it, here's the worst case scenario for what you are considering: You take the cash advance to raise your balance, the CCC freaks out and takes AA on you before you have a chance to pay it back, and then the High Balance never gets reported because it was never an actual statement balance. In that case, you're left with a freaked out CCC and are no better off as far as the CL goes than you were to begin with.
It might be a good idea to test the waters, so to speak, by trying it out with a smaller amount, but one that is still higher than the current High Balance, and see if you can force it to update. If so, then it might be worth a shot to try and force it even higher.
