Routed the edge of a piece of hardwood flooring with 1/4" roundover bit for a bending block. Moved layout of horn to other side of aluminum plate to 1) allow a deeper fit into vice and 2) provide longer surfaces (more leverage) for bending the horn/bearing flanges. Rough cut notches to separate the horns from the bearing (I found that my sabre saw works better than my band saw for these kind of cuts). Used Larry's bend line spreadsheet to determine the proper sight line which turns out to be about 3mm from the bend line. Initially I tried making the initial bend with the bending brake by placing the form block between the top and bottom brake plates with the part under the block. I was able to get the bend started but after only a few degrees the top plate began bending instead of the part. Rather that risk deforming the top plate on my brake I opted to mount the part in my vice between the form block and another block of hardwood. Used rawhide mallet to bend each section over the block. Was able to get the bearing flange to 27 degrees and each horn to 15 degrees. Will finish this part in next work session by cutting off excess material, smothing radii, cleaning up edges and drilling holes.
Thanks to Ron Lendon for his tip on bending over a block in the vice.