I just purchased a Kubota L3560 HSTC with delux cab and found myself on this board with the same seat issue, in taking the time to share here we go. Attached I provided my version of temporary solution in the form of what may have ended up as 3 pool noodles from dollar general made of foam stacked and tight as possible packed between the suspension vertical arms. After mounting as a 330lb guy I noe only sink 2 inchs approximatley and remain in a stable operating position of comfort, bottoming out not possible. I understand the foam will inevitabley compact or degrade thus temporary, in contrast compared to the tennis balls i find it very accessible, cheap, and i can pack two more in when the room becomes available. In the next two weeks I am ordering some trampoline springs testing to replace the stock springs and share finding but it will not be a solution to the shock absorber...when I find a replacement of appropriate dimension I will share in a follow up. Their areblimited components that will chew the foam and on the concept of a normal seat it came to mind for testing. When you do ride over rough terrain it gives an inch or two making a more firm but higher maintainable seat position for anyone 6'1" and above