Thanks operator.
As I said before, a vertical dropout is what I have to work with. (And it really is perfectly vertical-unfortunately.)
I don't think I would use a chain tensioner though unless I absolutely could not get the tension fixed with 1/2 links and tall toothed cogs. But first I would try other cogs and chainrings. I know they work fine but there is something really irritating about removing a clunky derailler and then putting something that looks just like a derailler right back on the bike. And I have read enough people's reports of succesfully using the magic gear that I will at least attempt it first. If the chain stretches too much; I'll get a new chain.
I can always put a Singulator on later if it doesn't work- or if I plan on taking the bike off of my home town boulevards out into the wild. I'm assuming they're just bolt on devices. Maybe it's something I can chuck in my toolbox and only use when seeking mischief.