Hi Volks,

From a TD point of view the solar shower accepts light which heats the rear
surface.  Unfortunately both surfaces are in contact with convective cooling
via the airstream  and  in contact with the cooler fiberglass tub when
you're driving.  If you wrap the SS in clear bubble wrap   You reduce the
radiant heating effect a little but you greatly reduce the convective
cooling and ... get a hotter shower.  Aint' science fun?

pensioner