Dancer is 30" tall and I have been driving her for 2 years now, and I will probably drive her in the shows this year. I use a Jerald cart that can be converted into a roadster cart, but I never have converted it into roadster. She has never struggled with it, but she used to struggle with our old Meadowbrook cart. It was very heavy, even for our 37" mare.
I've noticed thats sometimes when the sand in an arena is very deep it makes it harder for the smaller minis to drive!