My buddy and I use a Dodge Ram 1500 Pickup with Extended Bed. So far, we've hauled just one pin at a time. We haven't yet tried to see if/how two or more pins may/can fit at the same time.
And we've hauled with the legs still on and with the legs off. I guess with legs off seems like it should be safer in some ways, but everything was okay either way.
Just make sure you have plenty of moving blankets, water-resistant tarps and ratcheting tiedowns (be careful how tight you crank them down).