Hello Chip,

X3 screens are written to be able to dynamically reformat themselves depending on the screen size and orientation, etc.   This allows the same screen to appear in a readable format for users, regardless of whether they are using a mobile, tablet, or desktop with a 4k screen (for example)   

This means that although you can influence the screen layout and sizing to a degree, you cannot nail things down explicitly as it kind of decides itself where it needs to put fields.

Take a look at the authoring (Page customisation) capabilities for that particular screen to see if you can jiggle the fields around enough to make any difference