I should also mention for the benefit of those that haven't been around long enough to remember all the discussion around this, but I'm using an electric water pump (actually I'm using 2 of them) along with an electronic controller.
So with regards to the over-cooling concerns with the oil, if I find myself in this situation (possible in winter flying) the controller will slow the pump speed to keep the heat up.
I actually had experience where during winter flying as I would begin a long descent, the controller would cut back the pump speed to minimum in an effort to maintain engine temps which resulted in no cabin heat and damn, did it get cold fast! Really cold! And hard to put a jacket on in there. So I added a really small electric boost pump in the heater line which will maintain cabin heat.
Todd... winter is coming!