I have a good exhaust guy who has done some nice custom work, so I think I'll take the pipes off and see what he can do with them. I'm not going to wait for Morgan to reply to the dealer, as otherwise I'll miss the entire summer driving season...
I've been involved with trying to re-weld and reinforce a Brooklands system, including fitting flexible joints. Even though we really thought that we had done enough to repair the boxes and deal with the inherrent weaknesses, they still cracked in service. The conclusion is that the original materials and construction methods are poor and repairs never hold up. Therefore my advice would be to go to your 'good exhaust guy' and have new boxes fabricated. In your shoes I would also be tempted to have flexi joints incorporated into the new boxes (à la Garage56). Belt and braces etc...
