Not the same thing, but I'll throw this in the ring -- the only time I get cramps at night are when I'm dehydrated. I've also noticed my partner gets pretty bad muscle twitching some nights, and I'd be willing to bet quite a lot that those are the least hydrated days. Good luck in any case!
Sit bones = ~135 mm, saddles that work ~ 155cm/6.1 in wide
2003 da Vinci (custom road/all-rounder)/Terry Butterfly Ti
1994 Gary Fisher Nirvana (vintage MTB/commuter)/Terry Butterfly Chromoly
1991 Terry Symmetry (NOS frame/fork, project in progress)
1973 Raleigh Super Course (project in progress)