Jim: My 7800 may be an inch or two higher than the 7510 but assuming that the hinge is at about the same point on the ROPS, the height of mine, w/ROPS folded is probably about 5 1/2'. If you need a precise height, let me know and I will measure tonight and post it.
I have to fold the ROPS in order to get the tractor into its temporary home; my workshop/garage. Folding is pretty stiff (my dealer says that it will loosen up a bit over time) but not all that difficult. You take out two "hairpins" and unscrew two bolts before folding down. ....takes no more than a couple of minutes and is no real hassle to do when taking the tractor out and putting it away. I do it while the tractor is warming up at start, and idling prior to shutoff before putting away.
Hope this helps.