LISTEN TO THIS MAN!!!! ^^^^^^^
Cast acrylic is a freaking DREAM to work with after you play with extruded.
Cast is good for some things, but grinding it down on a sander ain't one of em. I have a few pieces around here that have cost me a few degrees of sanity (and a few burns as well) since acrylic heats up like a *******.
Square rod helps when you have a lot of angles you want to make. Round rod kinda skips around on the sander a bit.
I flame polished mine, but you have to be REALLY careful otherwise you set your last 4 or 5 hours of work on fire, or worse, cause it to get bubbly and then have to redo the whole side again.
Chris