All this is interesting,I talked with a guy around 3 months ago who bought a new super 60 37 and he said the same thing. He claimed the new hydro system was way to touchy and the mower rode like a tank. Puppy say's his 72 is great with the flex forks.
I demoed one lightly today for 5 minutes and I noticed the demo had flex forks on it and that tells me maybe the new chasses is over built and needs some flex? My 72 XR7 model rides grest stock and I noticed today a stiffness about the mower chasses but with the flex forks it seemed ok but I did not like the bounce of the front end.
When you run at high speeds over rough ground a little flex in the chasses makes a machine much more compliant,just not a mower any machine.
So when I see a demo Super with flex forks that tells me they may be trying to hide a problem with the ride? the mower is built great but it may be over built.
Honda found this out in 1997 when they redesigned the CR 250 and made the chasses to stiff for moto X. World champion Jeremy Mcgrawth told Honda to stick it up the butt and he immediately signed with Suzuki because of it.
It is not your imagination at all,if a machine is to stiff when you are going at a good clip it will beat the crap out of you. 15 MPH is a good clip!
Maybe air tires in front?
I am real interested in this because I am interested in one,all dealers who sell these along with multiple other brands say it is on paper the best quality designed Z ever but they are not using them on a daily basis.