Since the consensus seems to be that the rear stock caliper is inadequate here is my idea for a upgrade. Due to the availability of stock calipers why not use a pair of front calipers on the rear. Use the stock rear caliper for the E-brake and make up a bracket to fit the front calipers in the rear. Do the proportioning valve mod in the front, and put a ajustable proportioning valve in the rear circuit. Has anyone tried this and your thoughts?