TonyJ
Yes, I have a Twine shower in the Puma.
This is now the 4th vehicle that I have had this Shower installed - works great every time. In cooler climates we generally shower when the engine is still warm from the days drive; in warmer weather there is no need to even have the engine running.
There are some photos of the install here:
Landy Build
The water is usually sourced from an undercar tank, so we can have a shower after a bike ride.
I can also recirculate the water in the tank whilst driving, but only need to do so if we are in the High Country in the middle of winter and the water is really really cold (i.e. one cycle through the heat exchanger does not make it hot enough).