The main difference between the BX-32 and 42 -- in terms of what the tractor can support -- is the size and shape of branches you can/should feed in. I can see how it's possible to overload a tractor more easily with a 42, but that's about it.
Used sensibly, the 42 should be fine on a 2520. I run one on my Kubota
B2920 (21 HP PTO) and it works like a charm. I generally only chip stuff smaller than 3" diameter; anything bigger goes to the firewood pile. When chipping dry branches, I try to send a green branch through every once and a while. I chip beech, oak, maple, and pine.
Just because the
chipper is rated to 4" diameter doesn't mean you need to feed it that way; in fact, the main benefit of the 42 to me is that the feed chute and 4"x10" opening can more easily accommodate branches that might be crooked, twisted, or in bunches. That doesn't stress the capacity of the tractor or
chipper, but it does significantly improve productivity and workflow. Given the prices, I'd only suggest a 32 if the 42 was physically too big. The 42 is a better value, easier to use, more productive, and will have much better resale appeal. Just don't hook it to a tractor on the low end of the HP range and then send an oak 4x10 through the chute!!
