This is a 24" with all the seatpost that I am willing to expose. Riding it a few miles isn't ideal, but doable. If this was a 20"- I sure wouldn't ride it with any regularity on the road. I would pass on your BMX idea as originally posted.
I don't ride it sitting down. The seat is basically a rest, so that I can relax with my feet flat between running jumps/laps on a BMX track.