I reckon I haven't a clue either, but all my instincts are telling me to err on the side of caution. I reckon that means no.
Look at it this way - if contractions
are permissable, those of us who
don't employ them will (maybe) get extra Brownie points. Where do you draw the line? Would you say, for example, that 'ain't' counts as a four-letter word in place of 'am/are not'? I don't think it does.
Of course, my opinion could be a total load of _ _ _ _ (Substitute your own four-letter word.) What do I know?