tilt-bed wrecker option
When I initially moved from garage to airport, I hired a tilt-bed wrecker to haul everything but the wings, which I hauled one-at-a-time hanging the end of my Ranger-sized pickup (with wing spar going through the rear window into the cab.
When it came to hauling things back to my garage-based paint booth, to avoid the $125+ for each wrecker ride, I borrowed a flat-bed trailer. The problem with just about all of said trailers is that the wheel wells are just a few inches too close to let the main gears slip through. I removed the wheels and invested about $50 in Harbor Freight Aerospace 10" wheels, bolts, and angle that allowed be to replace the main gears with the narrower-track wheels, and had a net savings of about $200 in the process. If you are planning on hauling the -12 all over the place, I guess a dedicated trailer is in order, but if just hauling it to the airport, the tilt-bed wrecker is a reasonable option.
Nice to hear that the flatbed worked for David--my measurements seemed to always come up and inch or two too large.