None that I know of. Like I said before, the bridge on Carvins is adjustable, so you may be able to get a few extra tenths-of-a-millimeter out of each string.
Has the OP tried 16.5mm? I normally play 19mm 4 string, and 5 strings that are either 18 or 19 mm, but I didn't have much trouble adapting to the 16.5 mm Carvin uses on their sixes. Just a matter of getting used to it.