They seem like they do not roll very smoothly...... I donno, but does the added weight of the log decrease or increase they pushing effort?
I started this thread to show my approach with a simple sled and the roller supports, so I have no other reference for the effort needed to push the log thru. I do know that without a sled, just pushing a 10" thick piece does require some effort.
A suggestion, if you make another version would be to use a HPL like Formica on one or both of the sliding surfaces and with a spray silicone or wax, I think it will slide very easily.
Another suggestion regarding the 2 camera Video which I found difficult to watch in either of the 2 views. A person who could video you while you operated the sled would, in my opinion, be much smoother and easier to watch. A head mounted camera is just too jumpy to follow because your head moves each time you look at something else.
You have given the whole concept of milling with a vertical bandsaw a lot of thought and that comes thru loud and clear. It is a complex operation in some ways, but simple in others. I like the idea of having a long removable rail which is not attached to the saw permanently. This frees up the saw for other operations. I do know that lifting heavy logs is dangerous and cumbersome and any means other than using brute strength is great! I appreciate all your efforts.