I am coming into this late in the game so forgive me if I miss something.
Do you want to build this log arch for just on the farm use? Or are you planning to tow the log down the highway? If it were the latter, would a simple light bar on the end of the log qualify as legal in most states? The reason I ask this is I have access to a log arch that was built 50 years ago to handle 42” logs. The owner of it tells of bootlegging a pair of 12”x 24” 60’ bridge beams back from the coast (100 miles) by strapping the front of the beams to the frame of the dump truck that was towing the arch. Mind you, this was a couple of decades ago.
I my self have use for one for the purpose of picking up a choice log now and then and driving it home. If making it street legal is an option, even adding eclectic brakes and a light bar on the end of the log if necessary, it would be a lot easier then loading a log onto a high deck. As well as the fact that my half-ton truck gets a whole lot better gas mileage then either my big gas guzzling boom truck, of the one-ton crew cab with a 460 that cannot pass up a gas station.
Thanks for letting me in here I hope that I am not :deadhorse: