I would not think you should have any problems on handholding lenses in the focal length, as long as you remember not to shoot slower then the focal length of the lens, I regularly shoot upwads of 300mm lenses hand held with no problems, but if you stick to the 135mm needs to be at least shot at 1/150 or faster, you should be okay, practise your breathing techniques and you should be fine, when I find myself getting shots that are soft, it tells me, I am shooting to fast and my technique has deteriorated...

Dave