I am 52 and weigh 275 lbs, I like to ride hard ... my choices might be different if I was younger and lighter, but I am not.
Horrid ... small no suspension bikes will bang the hell out of you, I can feel my spine compress up to my head, that cant be good.
Some handle very squirrely ... my brothers Pacmule feels that way to me.
Sweet: Heathkit Hilltopper ...
Adult sized but still a mini. Wide long seat, suspension on both ends, wide cushy tires, handlebar and peg placement are very nice.
Its not as refined as say its competition when new, the Honda CT 70 but it has the mini bike motor and salsbury drive that keeps it firmly in the "real" mini bike family.
I also have a Heald VT10 ... its a great bike but its large and a bit to muscle around ...