I had the same idea. I bought a manual strap binder with metal crimps off of Amazon but haven't tried it. I was going to use two sides of my grapple and secure a 10 foot box against my corner and brace fence posts to get a squeeze on two sides, then I was going to use a super heavy rachet strap for the entire 10 bale set to try and get 4 sides compressed. Once that was done, I was going to release the grapple and then bind the set with the plastic strap binding I got off of amazon. I was then going to set on the trailer then release the rachet strap. While it may not be super tight, it would cause them to not fall off. Of course, you would still need big ratchets going across each 10 bale stack that would be 5+ high. The one concern I had was if the strap broke while in transport due to shifting, bumping, etc. It seems that the grapples that do the twine around the bundle use string and far less susceptible to breaking. If you could get a good compression, string tie might be cheaper and better. You just need a good knot. Let us know if you get something to work. Hydraulic table would be good and could do all 4 sides, but by the time you buy all of that, you would be better off with the grapple that ties in my opinion.