okay the tarp over the bent on the roof rack was not a good idea for all kinds of reasons listed. Try this idea...use a Bike Box, the type you'd use to ship a bent in a Jet. Some are made quite strong and have locks. Just lock the bike box onto a car/van roof rack and maybe add an alarm system to the box in the event anyone tries to force the lock. As for the size of bike box, I'd think if you did not want to keep taking your SWB or LWB apart, get a box designed for a Tandem. This has to be a cheaper alternative to buying a new vehicle everytime you change bents.