I've had the 67 coronet in a 20" trailer that I borrowed, but would never buy one that small for it. Front end is past the curb side door opening and have to squeeze through to tie the front down. Also barely room to work in front of the car (less than 3 ft) to work when tying it down.
I bought a 28 ft when it came time to buy, as I wanted cabinets and tool box.
Before I bought mine, I walked the pits at the winternationals and talked to lots of sportsman racers. Never talked to anyone that said they wished their trailer was smaller, but LOTS said they wished they'd bought bigger.