Originally Posted by TandemGeek

Bottom Line: If what you're conveying is that you have discovered the left-side cranks are right hand threaded, then you've got a "cheap and easy" cross over crankset on your new, used tandem. As for using SPD pedals backwards, I don't think I've ever seen any where it should work: the left and right hand pedal engagment and release mechanisms are asymetrical.