7/16 tubing bender: suggestions?

I need to bend some 7/16" (OD) soft copper tubing. The coil spring bender I have just won't hack it. It's all I can do to bend it with this by hand, I can't get a radius tighter than 2-3 inches, and what I get looks like hell. The "three sizes" die bender I have only goes up to 3/8". I haven't been able to find a rental shop that has one for this size. I tried to make a bigger bender out of hardwood, but it just flattened the tubing. I can buy one on Ebay for around $30 with shipping, but I only need it for this one job. Before I spend a couple of hours in the shop making a proper die, I thought I'd ask you experts. Anyone have any other suggestions? I know they fill music instrument tubing with ice before bending it, but they still use a die type bender. I've seen filling the tube with sand suggested, too. All ideas gratefully accepted. Thanks. I need to make at least two 90 degree bends and two 45's, all with around a 1-1.5" radius.