What's your intended delivery format? NTSC Standard Def is 4:3 only. PAL is 16:9...but NTSC, 4:3 only. There are 4:3 Anamorphic formats, but then it's squeezed and need to have a player that unsqueezes it. Or there's 4:3 letterbox.
My intended delivery is web (using Brightcove video server).
The video players are all 16/9 aspect ratio, and they do accept HD.
But because this is over an hour long speech, (and for web-playing purposes, HD is not so important on this piece), I usually downres the output to lower res. I always did that in FCP export for quicktime conversion. This would give me several widescreen resolutions to choose from, and they always would playback in widescreen.
So now I'm using AVID and the quicktime options look pretty much the same as FCP. But then the output is squeezed to 4/3.
I have the academic version of AVID, so I don't think I have Sorensen Squeeze or Encore.
Does that answer your questions and give a sense of what I'm trying to do?
I would output the reference movie and download mpeg streamclip. Its free, and will allow you to force a frame size on the quicktime it creates. I'm actually doing an SD project right now that is all 16:9 and has many quicktime approvals going out. I use reference and Squeeze, but there is no reason Streamclip won't do the same thing.