With the way you have already modified the trailer I don't think the fender mod would be much of a problem. If I recall how the fenders are mounted, all it would take would be a few short, flat pieces ot metal with a few holes drilled where needed.

The only prob with the smaller trailer (the one I have), is it didn't seem stable enough for multi level kayak hauling. Might have made it too top heavy. Future plans include diamond plate floor (for weight) then a system similar to yours to haul 4 kayaks with storage boxes below. The extra weight should make it stable enough for higher storage.

Great idea with the fence posts. Would have been cheaper than what I did. Oh well, maybe next time.

Has the lack of the smaller spring made a difference. A friend of mine suggested that during the building process but I chose to keep it. It made sense to a point. I thought it may cause the trailer to bounce more.