Broken Customline

My 1959 'Starmodel' Customline blew its rear uni joint again! I failed to mention it sooner. But the Cusso has been in the rain and off the road for a few months now. This is the third time that the rear uni joint has let go on me. When I initially replaced it. (due to being worn out.. I thought.. hmmm) It only lasted about 3 months of intermittant driving before it dropped on the road the first time. I reacted with anger over this event and blamed the mechanic who had fitted the first uni joint. However, this is now the THIRD time that the tailshaft has hit the road. Always the rear uni joint letting go. The problem must be the angle that the diff is connecting to the uni joint. The connection must be stressing the joint and wearing it rapidly. If the duff wasnt mounted squarly onto the springs. If it was out even just a little it could explain why the uni joints seems to only last a very very short amount of time. So I am waiting for my tailshaft to turn up. I was expecting it to be dropped off here by now. I will have to chase it. Having to see the old girl out in the weather each week. Watching the rust bubbles slowly get bigger is driving me nutz.