Mine came with pins, not bolts. They don't look to be particularly hard, but I could be wrong. They also have cute little springs that will launch across the yard when you pull the hairpin keepers. Not sure what the springs are about, but maybe Kubota didn't want the pins to rattle. I didn't really notice, and it took a while to find the first spring when I just taking the ROPS down to see how easy it was to do. I put my hand over the second one and caught it. I'm fairly quick to adapt. The hairpins are hanging on aircraft cable loops so I don't lose them, but that doesn't do much for the main pins, does it? (Afterthought) I took the ends of the aircraft cable retainers and threaded them through the eye of the main pins, so now have both secured. Can't do that with the springs and washers, though.
The only thing I would add to my ROPS would be some good thumb screws to stop the damn thing from rattling. I'm not sure why Kubota didn't realize that a rattling ROPS right next to the user's head would be ever so slightly annoying. Kinda weird actually, because they welded the nut there, but didn't put anything in it. Not sure why a thumbscrew in the nut would be an option instead of a feature. Then again, maybe addition of the thumbscrew just hasn't made it to the assembly instructions yet, and the poor folks in the factories and dealerships are wondering what to do with all those thumbscrews that seem to be accumulating.