[jw-]

Ok. I got more info. There are a lot of places that shrink the pictures. Here's what I've found.

1. For size, it is best to go with JPG in the Docx file.
2. Convert from Docx to Epub. For this conversion choose the Default Output file. Not Generic eInk. This will still reduce pictures to no more than 1500px (ie. if you have a Word picure that is 2400px by 2000px, it will go to 1500px)
3. Edit the EPUB. Go to the picture and resize it to 1500 or more.
4. Edit the stylesheet.CSS - Find the entries marked Calibre12 <- with a number. Some of these are text formatting. But most of mine are for the pictures. They start looking like this:

.calibre12 {
display: block;
height: 359pt;
line-height: 1.2;
margin-left: auto;
width: 468pt
}

See the height and width are hard coded. You need to take out those lines. I'm still experimenting whether the other 3 lines are needed.

After this I compile to MOBI. When I view the document, the pictures appear to resize to the page width. Which is what I want.

So it looks like 2 things; 1, get the right Pixels in the Epub, and 2, remove the hardcoded formatting in the stylesheet.css.

Edit: It looks like all the contents of Caliber12 { } can be removed for images. Between that and learning that it is easy to re-size them in the EPUB file, my problem looks to be solved. I checked this on Kindle Paperwhite and on Kindle App on Android.