Well turns out I am *far* more nooby than I realized when it came to sprite sheets.. :D 

Up to this point, my whole thought process was that this guy would have an "upperbody" sprite and a "legs" sprite, and they would function independently for aiming / firing and moving.

(Like, if you were moving, the legs are doing one thing, and wherever you're firing, the upper body would do something.)

I must say this is a *big* step up from the original sprite, with all the shooty angles and that little firing flash on the body!

I hope I didn't come across as impolite or uncomplimentary; I fully acknolwedge my lack of proficiency with spritesheets. (I bought Aseprite and...it's so difficult for me to use, I usually just use Piskel instead. I feel like this is someone who buys photoshop but then just uses MSPaint because they know how to use it.) :D  You did good work; I didn't mean to imply that my lack of understanding / skill was a shortcoming for your work.

About the sheet and the partial frames....when you drop a spritesheet into Godot, you don't say "Here's how big the frames should be in pixels."  Instead you just say "How many columns and how many rows."  It always divides the sheet evenly.  So like this sheet has a blue bar at the bottom:

https://opengameart.org/sites/default/files/warpgal-anim-sheet-alpha.png

edit : I removed my text-based explanation and just put what I see below! :D