TM-
What makes that winch a dual speed? I see only one speed- as fast as your hand can crank it! The different rated line pulls are a simple physics thing. All winches are stronger on the first wrap, you have more leverage. The following wraps require more leverage, thus less strength... I didn't see a way to switch gears, so unless you know something that I didn't see, it's a one speed winch....
Carl-
If you make the outside width of the arch as wide as the trailer bed, you should be able to run more than one layer of logs onto the trailer. Especially if you can adjust the hieght of the arch. Contain the logs with keepers in the bed that won't allow the log(s) to move further apart than the inner width of the arch, so you can run the wheels of the arch up beside them and put more on top. If you can come up with some sort of system to raise the sides of the trailer bed up as the hieght of the log stack increases (i.e. progressively build it up with 2" stock or something) you will gain some room that way. I don't have a green log chart anywhere that I know of to reference, but something tells me it wouldn't be long before you maxed out a 6 ton trailer.
You will need 2 vehicles anyway, one for the arch, one for the trailer, so why not just cut the trips in half, and use both at the same time? Or would you make 2 trips in the beginning (one with the arch, one with the trailer and tractor), and 2 in the end, and just use one truck? It's getting late, and maybe I'm not thinking straight either, I dunno...
Dan