Because of the frequency of crits, we have changed the way we do it:
Any roll of six only has the potential to cause a crit. For each six an additional d6 must be rolled and a crit is scored on a roll of 5 or 6. Yes, it is an extra step in the game but once used to it, it does not slow us down in the slightest and the result is nice, ship's hull points getting pounded down in a grind fest with one or two crits instead of one crit in every six hits (average). It also leads to a longer game, which we enjoy and better campaigns.
-V