Is there an option, in Vegas 4, to have the trimmed files saved in regular wav rather then the Wave64? In the past I've been burned by saving with proprietary formats and would like to avoid that as much as possible in the future.
Sorry, No. This has been discussed repeatedly here. I would like a choice including *.pca, another proprietary format (Sony's lossless compressed) excellent for archiving.
As far as I know wave64 isn't that different to wave, it's used mostly to get around the file size limit with standard wave files. Once you go to above 16/48 it's pretty easy to hit the limit.
Hang on, have I missed something here, you can use .pca format, well it comes up in Render As.