<<<snip>>> OK, even with an alarm a few of us would still forget to close that pop
top.
But with a cut off switch how can one forget? One would really have to
have
a brain made of mush. <<<snip>>>

A warning light or buzzer would not be to difficult to wire up.  There are
several manufacturers of limit switches (Micro-Switch, Selecta-Switch)
that are small enough to mount either inside the fiberglass of the pop-top
or in the metal rim that the pop-top seats into.  The switch would have to
be rated for 12 volt and be normally open in the extended position.  That
way, the circuit would not be completed (closed) unless the pop-top were
down/closed.  A power source would have to be run to the switch, then to a
pilot light somewhere on the dash.

Too, the same switch could be wired into the ignition circuit thereby
preventing the bus from starting when the top is up.  A relay could be
used in line with the ignition switch and run to the limit switch.  When
the key is turned and the top is up, the limit switch (open curcuit) would
prevent the relay from closing the ignition circuit.  The drawback to this
is you would not be able to recharge your aux. battery, say, when camping
unless you close the top.

Any electrical supply house should have everything needed to do this.
Newark Electronics or McMaster-Carr could be accessed on-line to research
or order.  Might cost all of $35 to do.

I'm sure one of the electric wizards on the list could lay this out in a
matter of minutes.

Alan Bosch
& Phred ('88 Wolfsburg)