Don't ignore the Koller. A couple of guys who were skidder loggers in E. WA moved over to our steep, timber laden area. They bought a sale with yarder ground in it. They got a Koller. The two guys taught their dad to run the yarder, one went in the brush, and the other drove truck.
They did ok once they figured it out. Things were so desperate at first, they were asking me how to rig it up!! Which I know the theory of, but not the how to of, like proper way to put pins in shackles!
They had an extension on the tube and a small, Eagle carriage. They apparently made enough to feed their families. They ended up using their forwarder for a guyline anchor. That's about all a forwarder of that size is good for here.
One of our locally grown loggers liked the Koller but disliked that it had no cab. It is run from ground level, with some heavy mesh for protection. You can hammer together a "cab" with plywood and tarp. They are run from the ground so unhooking chokers can be done by the same operator without a lot of climbing up and down.
What kind of carriage are you looking at? The one video I managed to look at just had butt rigging, and you can't use that in a partial cut unless the trees are spaced widely. Other things to consider are how many guylines does a machine require? There are some places where sound stumps are rare. Deadman anchors take time and machinery to make.
I found the memory stick with my pictures on it, I'll try to find the Koller pictures and the little Thunderbird. The Koller used 4 guylines, I think.
