MAYBE that extra heat from the aftermarket non-double-skinned exhaust is heating up the back-end more than normal ?
The standard exhaust and pipes are double skinned for noise reduction (drive-by testing) and to maintain exhaust temperatures inside the exhaust catalyst (emissions requirements), therefore keeping the heat internal to the system.
My 2008 GSA has 75,000 km with no leaks. But I'm very seriously considering replacing the shocks (as I genuinely don't think they are all that good) with Wilburs ESA, as they have a 10% promo at the moment, which narrows the gap between here and direct to Germany.
Again, sadly I'll have to take my shocks off and send them to Victoria reducing my riding life. Hmm, wonder if I can afford shocks and ECU re-mapping

Himalayas Royal Enfield Tour 2017; Camp Cook-Off Winner 2017; Kennedy Ranges; Three Oceans Tour Australia; Hyden-Norseman Breakaways; R1200 series final drive repair; Mt Augustus; Bimbijy Station; Around Oz