you probably want a way to hold the burner in place when it moves into place. would be a problem if it moved and was between the 2 vessels. maybe thumb screws or indents on the rail? i would use 2 rails, probably round. it would simplify the plumbing, no need for splitters and separate ball valves, but you lose the ability to heat multiple vessels at once (back to back batches, heating water in both vessels at once).