Want to do the same thing. A lot depends on the capacity of the toyhauling area and exactly where the weight distribution falls. Example: Where and how much weight is going to be behind the wheels of the trailer. Even the shortest of the tiny cars
Smart car is 8'6" long, the Scion IQ is 10' long and the Fiat 500 is 11'9" long. Ranging in weight from about 2100 to 2400#.
The front wheels will be ahead of the axles, but how far behind the axles the rear wheels of the car makes a big difference.
I have a Work and Play 34FK, total cargo capacity is over 7000#, but I still have to figure out how much I will be able to put in the cargo area. The ramp is good for 5000#. The concentrated weight and CG(center of gravity) is the tricky part. Ask any load master who works for the airlines or Air Force...