I build a Kitfox Classic with a 912 80HP on it, to which I added both an oil thermostat http://www.aircraftspruce.eu/remote-oil-thermostat.htm
and a cooler thermostat (can't recall that supplier - but it was a similar apparatus).
Worked as a charm from day 1.
The goal was to save fuel and time in the colder season, and it was astonishing to experience what a difference these little buggers made.
I kept a firm eye on the temps during run-up: these things do fail, you know? But they never let me down.
As I understood a CVV isn't necessary in RV12's, I will see if hat goes for oil and coolant temps, as well. These thermostats don't take much space (they do take lots of hoses, though), although their weight is an issue.
Some year building or so before I can add something useful to that discussion.
Keep on building!!