Bill, this may not be a solution that you're looking for, but perhaps it could work for your purposes. Add two tracks of solid color black generated media above your video track using crop within the pan/crop tool, one track with a bar at the top, the other with a bar at the bottom. You do the math to figure out how thick the bars should be, depending on your source material aspect ratio in order to achieve 2.4:1 viewed video.
Assuming 16:9 source footage, for instance, the rendered video will still be 16:9, of course, but with black bars top and bottom, as if the video was shot in the wider aspect ratio. On a flatscreen TV, this looks perfect.
If viewed on the Web, the black bars could look strange since web page material around the media player might make the bars really apparent. In that case, you might want to set up the project in Vegas as 2.4:1 and render out that way. Haven't done this, so perhaps others will chime in with a best practice on this point.
HD is by definition, 16:9. If you have a specific application that requires the Cinemascope format, you should be able to set it in the project preferences.
If you're delivering the project in 1920x1080 or 1280x720 (both 16x9) you can use this mask on a video track above your video. It is broadcast black with a 1920x800 transparent hole in it for your video to show through.
Hmmm... if you set your project properties to a framesize of 2.4:1 (say 1920x800), then crop your video events to 1920x800 and render to a 2.4:1 framesize (in this case 600x250), it works.
If your original footage is 2.4:1, then use the "Match Media Settings" wizard to set project properties and customize your render template to a 2.4:1 framesize.
Sorry to take so long and thanks a ton for your replies.
Here is what I did while waiting for replies:
Properties
Template: Custom (1920x1080, 23.976 fps)
Width: 1920
Height: 1080
PAR: 1.3333 (HDV1080)
Then: Match Output Aspect in Pan/Crop
I only have a cheap DSLR and 99% of my "footage" is stills.
(With good sound)
I love this aspect ratio since only receintly getting BD and watching Reservoir Dogs/Pulp Fiction/LOR etc on BD.
So that AR what I want to produce.
I haven't tried burning to BD and playing it yet though, so maybe all is not roses.
I'll try a test render right now.
Bill