A friend of a friend is running one of those as a SS too, but instead of using a tensioner he's gotten himself some spare dropouts from gawd knows where (which bolt on on these frames?) and has filed them out to give a bit of horizontal adjustment. He's kept one set of dropouts standard in case his modified ones die, so not something I'd try unless you had spares too.
Oh and welcome by the way... I see this is only your second post!