Use regular slide out ramps and put them on the side of your trailer.
Drag the logs up beside the trailer and roll them right on up. The old
timers used to load logs like that with mules or horses way back when.
You may need to use a pully on the off side of your trailer to 90 the
winch cable. Go OVER the log and back to the side of your trailer with
the cable and the log will roll right on up the ramps. If you have side
rails get ready for you log to fall into your trailer though. My
trailer is a flat bed and I have loaded up to 3 layers of logs this way.
Bind the bottom layer b'4 adding another layer though.

jack