ok, so after much trial and tribulation, i figured out how to accomplish what i wanted to do... installed an antenna on the camper roof of my vw westfalia camper bus. it's actually pretty easy.
first off, the camper top has only 4 bolts in the mid section and a number of screws around the top that keep the front (separate) portion of the camper top on the bus.
i removed the dome light from the inside to take a look at the bolts. you can get at the them but they are not easy to get at. a portion of my camper top was cracked around the bolt, which make lifting it from the front fairly easy.
rather than fuss with the bolts and get the whole top off - on a whim, i decided to remove all the screws along the front/sides. this gave me just enough clearance to place an antenna mount on the inside (with the antenna itself attaching from the top).
the antenna mount for the 5/8th wave uhf/vhf antenna is just about a 0.5" wide. the drain holes on the top of the camper in the recessed luggage area are also 0.5" -- however needed drilling out for the antenna mount to clear the hole. so i got the drill out and widened the existing hole a little bit. the fiberglass is easy to drill.
for a ground plane.... i picked up a cheap aluminum cookie sheet at the store, along with two 0.75" metal washers. made a small hole in the cookie sheet (off to one side so it would fit properly when finally placed up on the roof) and "sandwiched" it using the washers in order to clamp down on it with the antenna mount. alright, had to get the voltmeter out (continuity tester) to check my work and make sure the antenna was conducting through to the cookie sheet. no problem.
other good news is the antenna i got has a flexible cable dismount in the base, so i don't need to *remove* the antenna like i thought i might have to, for just going through a car wash or parking by low trees. sweet. incidentally, that's a cb antenna turned down on the side (attached to the rain gutter) - i don't really use it.
