I had a Micron fitted to the XBR I had a few years ago. Very solid and an exacting fit with the pipe to engine manifold connections being fixed position (assumed they were welded in position?) but once aligned correctly it was a great fit. Copper crush sealing rings were used.
Other non OE systems I've had on XBR's (Black Widow & Predator 2:1's) have used the more common type clamp that uses a flange on the header pipe to pull against the seal. It seems that Black Widow have now ceased offering XBR items but I think that Predator may still be selling them. I contacted the chap at OS a few years back who would make a bespoke full 2:2 system for circa £500 (but note steel prices have rocketed since then) taking about a week but all the reports I'd come across say that are that they are very good quality. I wish now that I had bought the Motad 2:2 system for less than £300 before they ceased trading as XBR exhausts are getting harder to find.
I hope that you find a way of fixing your Micron in the interim.