Yea, unless you need/want a seamless fly through - outside to inside and back to outside and maybe right into a pull back or fly around, it just seems far more risk than it's worth to try to fly into a vehicle, even a big one. If it's just a pull out from inside to out (or vice versa), attaching Solo to a poll and just using it as a Steadicam seems like a much better idea. You'll still be able to pitch the camera up/down with the controller, and you could whip up a swivel so you could pan the entire solo if need be.
Keep in mind, in an enclosed environment, you're going to be generating a LOT of air currents which will effect stability in all kinds of ways. If you get too close to the roof, it'll generate a low-pressure bubble directly overhead and the Solo will get sucked up. You can see this flying a small (micro) quad or heli indoors - get within a few inches of the ceiling, it'll get sucked up and you won't be able to get it to come down until you drop the throttle WAY below that necessary to keep it in the air. When it finally falls from the ceiling, you have to gun the throttle to keep it from plummeting to the floor. Beyond the roof, you're going to have all kinds of air currents and turbulence inside that will make precision flying difficult to impossible.
Of course, with something the size of the Solo, it would probably get sucked up within 1-2 feet of a ceiling, and it's not going to just sit there skimming the ceiling, it's going to hit something, bust a prop and come crashing down.
Unless you're talking about some seriously large vans, I'm just not seeing this as a good idea, unless your intention is to destroy the Solo or money is no object and it's worth a shot in the chance that it actually works.
