flame inserted the file into the CMN.DAT file and came up with a rather disappointing result. First image is the original, second image is the translation of the text + a portion of the file you photoshopped (it's in the text box, under the unit icon):
There seem to be 2 major problems here:
1. Color: you'll need to use white text instead of black
2. Height: the English version needs to be the exact same height as the original, otherwise you get the above result. As far as I understand, the game summons certain text from a GIM file such as yours, but the address it "dials" to do this, is determined by its pixel location. So if it's even one pixel off, you get a shift in text that is displayed ingame like in the screenshot. For the same reason the width is slightly less important because if you made it shorter than the original, you'll simply summon some empty pixels along with the word. Just don't make it longer than the original. I hope that made some sense.
Honestly, I thought the result would've been better as well, but as you can see this will be a trial/error thing until we get the first one right. After that, things will go much smoother. The next issue will be choosing the appropriate font, but first things first.
PS: That big lump of Bydo sure was a doozy... One of the few missions I had to retry, even with savestates from PPSSPP. You'll also notice that I translated "GailRose" as "Geirrod" because it is one of many names derived from Norse mythology (other examples are Utgarda Loki and Glitnir). It's also depicted in one of the images in the captain's logbook I believe.