Question about 1st person weapon aspect ratio

[Solid Snek]

Hello everyone!

First of all, apologies if there is already an answer to this particular problem and I've just missed it.
I recently started modding this game, and I'm currently working on some new 3d weapon models for rendering. What I'm stuck with right now however, is trying to figure out how to get all of the CIF records to display correctly with the same aspect ratio and 320x200 pixel frames. The original idle, or 0 records especially, are too small for the weapon poses I have in mind.

As far as I've understood so far, I need to make .xml files to fix this, but I haven't figured out how to get them working.
Any help would be appreciated.