Thanks all for your replies. I have settled for a lesser-of-two evils option.
I cut the copper coming from the stack elbow back a bit further, and have glued (desperate times) a solvent weld elbow onto the copper using a large quantity of quick setting glue. The rest I have managed to get level enough using fittings. I will wait for the glue to dry and thoroughly test. If the one potentially weak point works then I'm out of trouble, if not it'll be back to the drawing board.
I cut the copper coming from the stack elbow back a bit further, and have glued (desperate times) a solvent weld elbow onto the copper using a large quantity of quick setting glue. The rest I have managed to get level enough using fittings. I will wait for the glue to dry and thoroughly test. If the one potentially weak point works then I'm out of trouble, if not it'll be back to the drawing board.
