When you have it non knocking (if at all possible) mark the joints carefully with a chisel or dremmel.
When it slips in a few months and starts rattling like a mofo all you have to do is line it back up

It is mark of a good exhaust fitter to cut and shape a custom exhaust to fit properly, most places just bash them on which does not stay rattle free for long even with the best materials like Miltek. Worth making sure your engine mounts are good as well.
Rear beam can be modified to give a bit more space, but this needs to be done properly and not just hacked out with a grinder.....
My exhaust was perfect on the first golf it was on, now it rattles like fook when its cold, very annoying as my daily drive is 4 miles each way, cars a £300 sh1tter and goes in the bin when the tax runs out in septemeber so I dont care
