Rubber suppliers, its readily findable online, i do a lot of smaller brackets this way with the exact profile, die finish greatly effects how stuck, i use about 5 degrees and they will pop out easy. A BFH and a suitable former is another easy fix for just 100 or so a year.
Getting the legs parallel takes a non flat top ie bend em past 90, that said, my parts end up going onto a curved item and the spring back kinda makes them self tension and pull down just right :-) That said, you will never get absolute perfection, steel hardness varies a little batch to batch, thickness varies and at best a solid form tool will only get you within +- a couple of degrees do to thoes variables. Hence the BFH correction device which goes pretty dang fast once you get the feel.
As a rule on this stuff i never allow any clearance, reality is sheets always about 4-5 thou thin over here and that gives me all i find i need.
If you want dead parrelel on the leg uprights its a lot harder to form this in one hit, far easier to rough form then pop a manderal in the curve and over bend it so it springs back to the perfect 180 degree as a secound operation, again do to material variations one batch will be diffrent to the next hence its easier and faster to just correct the low hundreds a year range that try to 100% it to perfection with one hit.
