It seems foolish to throw away a useful tool.
And simply no, I do not see a good way to tension it like you have it set up now, mainly do to the fact that springs in a tensioner will allow chains to slip.
Something like this could be converted into that tensioner from mcmaster mentioned earlier. I have never used this style to tension, I have no idea how they work.
http://www.mcmaster.com/#sprockets/=70knoq
The link isnt working here is the pn 6793K19