Well, after trying multiple ideas and ruining a couple of perfectly good DOM tube sections, I am about ready to make one last attempt at doing the large radius curved dash tubing.
I tried the bender board idea. I was able to bend a tube about 30 degrees before getting a nice kink. Should have gone a little slower - but even then, it does put slight dimples on the inside of the tube.
Next I tried making dies for the harbor freight bender I have laying around... again, slightly kinked bends, which I'm not interested in.
I'm going to try the proper way to bend it next... If this doesn't work, I'll move on to doing smaller radius bends with a flat dash bottom.
I need a couple more pieces to try a bend with this thing... Since the tubing is .050 wall, hopefully MDF is strong enough:
http://gickr.com/results4/anim_e4275fbb-3737-99f4-ddd5-73fe2fecdf2a.gif