One other way to do it is to place a toggle switch inline in the sliding
door contact switch wire.  Same idea as putting your thumb on the contact
switch.  Allows me to leave the slider open but not have to shut off any of
the domes manually.

I have a pic out at
http://www.weidefamily.net/vanagon/
browse to Electric > Inside Lights > Cabin & Dome Lights - Replacement and
Repair

Thanks,
Brent