Thanks for the tip. I'll keep it in mind for future work. Can I send you a .psd file so you can try it out on yours and see if there are any issues? Maybe it's a problem with the way my software exports to .tga?
In fact, anyone willing is welcome to try it. You can find the file here:
If it ends up working fine when you save it as a .tga, I would appreciate it if you would send it back to me in that form.