Well, I do my lift off at about waist height and my bottom stops are the length of my arms. As you can guess I dont do pendalays, just a regular bent over row. But I do a pause at the bottom. I really dont think it matters that much, just so youre doing the bbl rowing motion AT THIS POINT. Dude you really dont need to be quite so specific for now. Remember you are going for mass. Get the mass first and then refine the definition.
I work on keeping my back parallel to the floor. Then on the last rep or 2, I might raise up to about 20° or so. You can vary this to hit diff areas of your back.