Another option (assuming all 'through hole' components are being used) ...use double sided 1oz copper board, just arrange it so that your bottom layer is a replica of the top layer (so it would need to be mirrored)....voila you've got 2oz copper board for all your tracks!

If you're worried about alignment...just make sure your pcb board design has some index holes so that when you flip the board, everything will be aligned perfectly on the 2nd isolation run (and presumably this being a powers supply, your tracks are going to be quite chunky, which will be more forgiving for alignment)