We used to bend 90 degree angles in 1/4" plexiglass when making "covers" for desks at work, and the angle would keep it from sliding off the desk. Used a brazing torch and evenly feathered the flame back and forth above the plexiglass after laying it over the edge of a slightly rounded surface. Just have to keep an eye on it and go slow, and don't get the flame close to the plastic. A lot of radiant heat is out away from the flame. We also used a torch to "glass" the edges of freshly cut plexiglass to give it a smooth appearance. Just gotta keep the torch moving and don't get close. We did mess up a few times, but had plenty of backup stock. Practice on a scrap piece first.