I am using Vegas to encode video (4:3 material only) for the PSP.

My goal is to have a rendering of the movie in PSP native resolution, in highest quality possible, and the video MUST be able to run in "Full Screen" mode. By "Full Screen" I specifically mean the 4th mode (Original -> Normal -> Zoom -> Full Screen) of the PSP video rendering, i.e. 4:3 material is streched on the PSP-side so that it fills the entire PSP screen without distortion, by cutting of the top and bottom parts of the 4:3 video (this is intended).

When I encode a movie in Sony Vegas with "Render as…", I use:
Type: Sony AVC (*.mp4, *.m2ts, *.avc)
Template: Memory Stick QVGA - 1128 Kbps
Custom: Video rendering quality: Best

This will result in a video in 320x240 resolution, playable on the PSP, with all four screen modes (Original -> Normal -> Zoom -> Full Screen) functional on the PSP.

This is fine so far but I want to increase the resolution to PSP native resolution, 480 x 272. I can do this by manually entering the resolution, or by choosing any of the predefing settings/workflows for PSP encoding of Sony Vegas. However, if I do this, the resulting video on the PSP will only have the screen settings "Original -> Normal -> Zoom", but not "Full Screen" which is the one I also must have.

In short: when encoding movies with Vegas, if I select the PSP native resolution, the video can not be set into Full Screen on the PSP. This is only possible when using a lower resolution.

I wonder, is this problem PSP-related (i.e. is it impossible to get movies in natiuve resolution to run in "Full Screen" setting in principle?) or has it to do with the encoding? I would be thankful for any ideas how to fix this problem!

I am using Vegas Pro, Version 8.0b (Build 217). Target platform is a PSP Slim.