I have been using a cheap (Bosch knock-off, approx Can$30) adjustable
voltage reg in my van for 5 months now. It looks just like a normal
brush/reg combo but with a tiny screw adjustment on it.

I set it for 14.2 volts and it does work. Its holds that voltage (no
loads) pretty well, only dropping to about 14V when hot. And the unit
does get hot, whether more than the normal one I can't say. I was
worried about this heat but the thing keeps working.

I have a small 30 A/hr gel cell (house battery when camping) to be
charged along with starter battery and that is why I chose the slightly
higher voltage setting.

When engine is warm I get a reading of 14.1 up at the cig lighter. My
160 Watts of low beams drops that to 13.8.

Alistair

'82 westy, diesel converted to gas in '94
http://www.members.shaw.ca/albell/