Ha! thanks, John. I think we could knock this out in a Saturday, just need some angle and a mess of old roller blade wheels.
but yeah Bruce, maybe moving the axle is simpler, and it gets to the same point. How would one secure it in place, the spring hangers attached to a movable channel, with pins or something that slipped through the frame every 3" or so? How much travel would you actually need anyway, on say, a 14' long trailer body (excluding tongue, 10' camper + 4' deck).