The ROPS on my tractor was a standard non-folding ROPS. Before I took delivery, and since I had a backhoe and needed the height, my DEALER took the ROPS off, cut it in half, welded in 6" of additional height, made a hinge similar to the factory one, and put it back on. Done. No big deal.
For all of you guys who have a complex about getting sued, there is a little something called assumption of risk. If the guy who buys the tractor knows that the ROPS bar has been modified, he assumes that risk. He has the option of replacing it if he chooses. If he chooses not to, he assumes the risk. Further, what makes the original owner liable for a new owner putting a machine in a place that gets him hurt? The new owner is operating the machine, in what would presumably be in an unsafe or incompetent manner, and he is aware that a piece of the equipment is modified. At best it's split liability, if any liablity at all.