I went round to a friends house who's also a hobby moulder.  He's been having trouble with his mouldings warping.  They are CSM polyester and have moulded fine.  Over time (up to a year) they are warping really badly.  One example is a panel that has a 90 degree return / lip which has curled up beyond the 90 degree!  I've never had this and all I could come up with was demoulding too early.  Are there any other reasons he could be seeing this?