Well, I don't use a tub grinder, I just open the bales and spread them out in the mangers or in the bunk feeder. I'm a pretty small operation with only 30 milk cows and some heifers. My main concern is what twine would be better for use with the thrower. I've heard that the plastic twine is stronger and less likely to break when the bales bounce off the back of the thrower rack. I have noticed, though, that the plastic twine sometimes melts and breaks if the bale doesn't get pushed far enough out of the chamber such as on the end of a row or if the hay is thin. Does the sisal twine prevent that, or will it burn through just as easily? I currently have 4 full and 2 partial rolls of plastic twine left over, so I'd have to buy new twine in addition to the bill hooks if I got that route, but I'm willing to spend the money if it makes for less troubles down the road. I need to make a decision tomorrow when I order the bill hooks, so I thought I would get some opinions from folks with experience. Upstate ny, I see what you are saying now. I was thinking about the knot pulling off, not tightening up. I'm still getting the hang of the new knotter system.