I've got a 2005 Ural Gear Up - and I noticed towards the end of last fall that my seat was getting really, really soft and bouncy on rough gravel roads. On top of that, I was having to hold myself forward or I'd go sliding off the back. Clearly, this isn't how things are designed to work - so I investigated!
What was the problem? My seat support cracked, and was allowing far more movement than intended. On top of that, the rear rubber support ("spring"?) was old, and simply didn't offer as much resistance to movement as it once did.
How bad were things? Well... here's how far the support had cracked. It wasn't completely through, but it was getting there in a hurry.
Time to fix this! Fortunately, I know someone who is quite good with a welder.