Custom cutter, We had 2 self loading trailers. I made a "U" shaped bar out of 2" galv water pipe with an angle brace in each corner for side stability. Fastened it at the rear of the trailer with 1 bolt on each side and a bracket bolted to the trailer for the pipe frame ends "legs" to fit inside and hold the outer ends of the bolts.
Both trailers were built the same only 1 was 28' open frame and the other was a 10' decked trailer. We put a 12v 6500# winch on the top of the gooseneck in the front and a 3500# 12V boat super winch on the decked trailer. A couple of chains were added to adjust how far back from the end of the trail would give the log clearance to set up on the deck or open frame.
A short chain was added to the center of the crossbar, but, it WAS movable, side to side, so we could stack the logs appropriately all longways on the trailers. A snatch block was hung from the short chain and winch line threaded through and down to the log. We could drag the logs to the trailer if necessary, and raise the end up and set it on the trailer. Then, slide the cable back on the log and repeat.
We had 2 chains fixed to the end of each trailer, that would allow the "U" bar to swing forward and stop just short of "breaking over". Slack the winch line and the bar would travel back toward the next log, OR, just leave the winch cable snugged up and transport the logs as far as you needed to go.
Hit the forestry forum and poke around in my gallery for many pictures of what we did. I'm not good with posting photos here.
I even made a wooden one down here and loaded a 42" dia. X 12' Mango log with my wife as the only helper. We had quite an audience and not one person helped or believed we could load that log. Once on the trailer, I waved to the crowd and took a bow. Wife couldn't believe I did that.