Couldn't tell ya but the MJ system is really slick.
Just do like the Montana jack's set up. Make a couple of places to hook a chain to and use a chain boomer to hold them to the axle. (or ratchet strap although it wouldn't last as long). I do think that the sled style of MJ's would work better than the axle idea on rougher terrain such are step inclines and other logs.I do alot of log skidding with my foreman too.I'm trying to come up with something like that also.I'm thinking about building a log dray to be used in the winter,but I still need to come up with something better for use in the summer and fall.I've thought about a simple axle with car tires and a tongue to hook up to the Foreman,just not sure how to hold the logs to the axle.