Your 4:3 Sony "reads" any HDMI/720p or 1080i signal as an HD digital, whether the original signal was or not. Set up the way you have it, you can get it to letterbox all the time, or go 4:3 all the time, but it won't switch back and forth-the correction, if any, has to come from the HR20, and if that is not possible, the above suggested switch to component, or changing resoution outputs, should work fine. The HR10-250 will compensate for this, but our Sony TV won't. I leave it on 720p ll the time and the box makes the correction.
Sometimes, DirecTV's "progress" and new boxes come at a price, eh?