Hi bisc63, well when I was researching the Willow it was shown only once on a trolley and as others have commented in the trolley WIP, I used a photo of a model ( so I'm told) just to get an idea of what one looked like. I would imagine that they would have used whatever tractor or towing vehicle wherever the were at the time. Your Idea of a Kettenkrad would be about right because the rear end was tracked, am I right, to drag it up a beach or concrete slipway?