I have one alternative for you which will cost u practically nothing while u gain a bit more bass plus general increase in volume and also LTA friendly since it is OEM exhaust still :laughlik:
There should be a connector at your rear muffler, this controls the internal 'flap' to open/close as you step on the accelerator. The bigger it opens, the louder the exhaust gets. You can unplug it and it will remain fully open thus u get the max OEM sound/bass when even idling. Also, the cabin drone will be the same as when u full throttle your 35's current OEM exhaust.
Disclaimer: I am not sure if 535's rear muffler has this connection plug but I assume it should, since it is also a 35. This connector exist in the rear muffler of the 135, unplugging it, makes the exhaust louder too.