Re: rear suspension
Belt clutch you probably know can slip. Water gets on it it slips a while til dries. I've gone through small streams and then if it is a hill right away that sort of sucks.
I think the noise is pretty much the same. It is the bell and shoes, not some much the chain. I only have a 2.5 hp not 6hp. I may put a newer (still old though) 3hp Briggs 4stroke in its place if I can but shaft size is wrong from the edger I acquired.
My 2 jack shaft system uses 2 belts and one small length of chain. The belts and pulleys need cleaning after they get dirty and grime on them. I use acetone on the pulleys and mild dish soap on the belts then dry. It makes a lot of difference.
Your suspension sound like it works real good! I have only front shocks and for it I have a smaller tire on the front. I swapped in a 24 inch fork on a 26 inch frame, cause free parts are nice. It is level anyway as the shock keeps it level until I am bouncing and hoping not to bottom out. Bottoming out I have now knowledge that slowing and steering around is the way to avoid that. Trails I've not been on I first take them a few times slower to remember the big hazards.