Thats a good idea for your setup. On my tractor I was able to use the factory seat mount that has springs on the bottom of it actually take care of that problem.
2010 MF 1529, Woods ZTR MZ1952, National Mower sickle bar circa 1963
If the back is rigid, the springs and shocks underneath don't help with whip-lash. This can be a problem on rough ground and with hydro drives, as they will stop (or go) on a dime. Your upper body has to be flexible.
I sure I will find out what you mean soon enough. I have several horse pastures that need bush hogging but I am waiting on some wheel spacers and skid plates first. I can't imagine it being worse than the factory high back seat that I have used the last six years.