Ryan, the rule of thumb is go 3 inches longer than your current putter. Thus, you would consider a 37 or 38 inch counter balance putter.  37 inches would probably be the best fit though... you might experiment a bit though since this has a different feel so you may prefer a slightly longer putter at 38 but regardless 3 inches is all that should be above your hands to make the CB feel correct.

Good Luck!

You only need 3 inches above your hands so you may need a 37 inch counter balance putter!