I'm suffering the same problem to a lesser degree. I have racked my brain and believe my problem is the rubber lines. The brakes work good but the more I drive the hotter the rear brakes get. I too have rebuilt most everything. What I'm thinking is the rear rubber line is deteriorated enough to let the fluid through but it can't flow back fast enough to let the brake shoes pull back. I will be replacing all three rubber lines in the next week or so.
Bruce
