My 790 & Jinma combo will handle oak and other hardwoods up to 4" just fine. Anything over 4" is firewood. I set the RPM at 2600 and it tears through almost everything with only an occasional drop in RPM on large dry trunks. When that happens, grab the roller clutch. That stops the feeding, let the tractor catch up a little bit for 4-5 seconds and then resume chipping. The 790 has about 24 HP at the PTO. That is about the lower end for the Jinma if you chip anything over 3". It would be awesome if I had 30-50 PTO HP
It will tear through pine up to 5.5" without hesitating. Feed it a pine trunk that has been delimbed up to 15' long, step away to go get another piece of wood and when you turn around the pine tree is gone.
Always feed large end first and wear hearing/eye protection at all times.
The only negative on the Jinma is that it is not a shredder. I personally don't understand why anyone needs a shredder. I take limbs and convert them into neat little wood pieces. Oak mulch is very pretty once you spread it and it gets rained on once. Very light colored and clean to walk on. The pieces are large enough where they don't stick to your shoes like cypress mulch does.
If you chip pine, lay that mulch first then top dress with oak chips.
If you have a pickup and pallet forks or a low trailer, pick it up at a freight depot and save a bunch of delivery costs. Easy to assemble without a helper in about 3 hours. Less if you had an extra pair of hands. Half of that time will be taking the steel crate apart and getting the pieces unbolted from the crate. The FEL can lift it out of a pickup if you have forks.
A lot of us here have Jinmas. As you can see from my profile, I am JD person but had no qualms about the Jinma
chipper. Just make sure to order yours in the available green & yellow color combo.