Received my Woodmaxx 8 Mechanicl Feed PTO chipper last weekend, took 3 hours to assemble and have used it for about 8 hours on my 28Max and does a great job. Well engineered and built chipper for any money. 28 horse is about as small an engine as I would put it on as I have close to stalled it on a few 5" maple limbs. Keep em under 3' long and it is OK.
I got my Woodmaxx just like yours about 2 months ago. My assembly was a little more challenging as one of the panels was a little bend during shipping. But the Woodmaxx folks (thanks Amanda!) were great at sending me the replacement panel at no charge ASAP. I only have about an hour of use on my 4035HST. I was able to do some 6 inch diameter logs just fine. I never stalled the tractor, but I did manage to get a couple of pieces stuck because I was being just a little too aggressive with what I was feeding. But it gave me some good experience with clearing jams! Overall very happy so far!