Rocky,
My buddy has a MCSB with the Ram Box towing a 5ver. While he doesn't have the sidewinder setup, he has made a PullRite auto slider work. So I don't see any reason why the sidewinder system won't work. He had the pin box modified and reinforced to clear the bed rails, and had the 5ver ('11 or '12 Puma) lifted 6" to level the 5ver out.
He would have gone with the sidewinder as all the research said it would work with the Ram Box, but the salesman assured him that PullRite said it would work. It did, after an additional $1000 in modifications the dealer wouldn't cover.
Hope this helps a little.
Good luck!!!