Oh I would agree that we need to change formation. IMO we need players on both flanks who have pace, can beat a man and get a cross in. Petra continually needs to stop and switch to his right foot to get a cross in when played left which negates the fact that he's beaten the defender for pace in the first place. I wouldn't be against him as a RWB. He, in theory, has all the attributes for the position. Fast, strong and can cross (sometimes), his positioning would be suspect when defending however and he would need to learn to tackle so it's possibly a step too far to play him there just now (and let's face it, McKinnon won't do that, or play Robson for that matter.)
We need to create more chances, it's not happening with over reliance on the likes of Paton and McGhee to supply them.