Did you ever figure out what was wrong with your marathon/truck issue?
IMO the leg design is weak. Add in that the deck is bolted into the box at the bottom of the legs. Gives no support to keep the deck steady with a load on it. The paint is gone on the edges of my box rails where the deck was hitting it from swaying soo much. There was no cracks when the deck was put in. When I finally pulled it out one leg was starting to crack. Not on a weld but on the leg itself. The crack was caused by the swaying not the other way around. This was very minimal use on this deck.
Since I've switched to CrossTrax I've had no issues at all