Hey, okay if you want to avoid Horizontal and Vertical Masking and you must have the mask, then you should go for a 4:3 aspect ratio panel.
Now, if you are worried about not having the number of Vertical Lines of resolution (ie number of pixels) then consider this: no matter what, any HD image will have to be scaled to fit any UXGA or SXGA or XGA device. That being said, of course you want a panel that will have enough lines of resolution in the 16:9 area to match as closely as possible the HD output source so that scaling is minimal. So, consider whether you will be receiving a 1080i or 720p signal when looking at the resolution of the panel you pick. For example, if you are receiving 720p, then an SXGA panel would probably be okay. Obviously, an idea panel for HD would be 1280x720 (like the HD2 Mustang chip), but you would have to calculate the resolution of 4:3 chip you would need to have 720 lines (or 1080) in the 16:9 area.
Does that make sense or help in your thought process?