Original 3x3x1/4" angles were returned to vendor and exchanged for two 2.5x2.5x3/16" angles (for bottom and bending plates) and one 2.5x2.5x1/4" angle (top plate) - 10' long each. Found that these sizes are much straighter. The lighter weight is an added bonus. Also purchased a 1.25" square x 1/8" wall thickness x 12' long tube for handle fabrication. These along with my two 0.060" hinges and proper bolt/rivet spacing should provide adequate strength to produce accurate, straight bends for all metal thicknesses/lengths.
Since most parts do not require the full 10' length of this brake I'm considering cutting the bending plate in two, essenitally forming two side-by-side 5' brakes that can be joined when required to make the longer bends. Still working through all of the design implications before committing to what may turn out to be overkill.
6/19/11 Update: When bending the 6T1-4 Rear Stab Spar the 2.5" angle works perfectly. Image #2 shows how the first bend flange fits over the bend plate. It was fortunate that I went with this size.
