If I recall correctly, the 7510 has 16 HP at the PTO.
Well, I ran a 60" (5 foot) Land Pride through some very thick brush...much of it was as tall as the tractor.
This was with a Deere 670 which has about the same horsepower as the 7510. I bought this Land Pride from a dealer who sells Kubotas. He did tell me they sold the 60" cutters with the 7500's. Now, that was a salesman, but he seemed pretty straight up. And the dealership, like many in PA, is looking for repeat business...very much a family type place.
If you use common sense, I think the 60" cutter will do you fine...it'll be slower going then with a 48" cutter, most likely. But if you're in thick brush, you'll be going pretty slow with either size cutter.
FYI, the 790 I have now doesn't do that much better then that 670...just recovers quicker when it bogs down...probably doesn't bog down as much as the 670 did.