John, you didn't say what version you're building, but anything less than a RV-10 will fit nicely in a medium size car, provided the rear seat will fold down, the right front seat will recline, and it's open thru the trunk. I hauled my -7 back from there in a Chev Malibu, but could have done it nicely with my smaller Mazda MX-6, or the wife's Camry. The horizontal stabilizer (RV-7) measures 100" wide by 24" front-to-back, and about 4" thick. Fact is, I could have put two sets in this car! Remember, the elevators won't be attatched to the horizontal for the trip home. The rest of the parts will lay on the remaining trunk floor, rear floor, etc. Bring some blankets or sleeping bags, pillows, etc. from home to wrap and cushion things on the ride home. If you're in doubt about if your car will haul these parts, simply make-up a cardboard box or something to the above dimensions and try it in your car for size. Remember that the horizontal stabilizer tapers towards the ends, so the front-to-back measurement only applies in the center area of the part.
Have fun up there and happy building!
P.S. You will be at it from 8am till 8pm for 6 days and probably a few hours on Sunday also.