They make acrylic specifically designed to be heat-bent, it works MUCH better than bending basic cast. If you can't find any close by, Regional Supply will be happy to ship you some!
for bending, I made a fixture once that worked pretty good for heating plex and Rowmark for bending- it was nothing more than two 1/8" thick aluminum plates about 2 x 8", screwed to a couple of 2x4 'legs', with a 1/4" or so space between the plates. I marked the plastic (tiny speck of post-it note works) where the bend was to take place, then held it in place under the aluminum with the bend marks centered in the slot. Then I ran a 1500w heat gun across the slot for 8-10 seconds. The area to bend gets plenty hot, and the slot localizes the heat nicely so the plastic doesn't distort beyond the actual bend. If you don't want to just hold the plastic in place, stack up a few wood/plastic scraps to make a shelf. But I found keeping the plex against the aluminum localizes the heat better--
looks kinda like this
Attachment 361595