Effects Window Icon Spacing Woes

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I decided the other day that I was bored with the top-to-bottom maintained and effects windows, and wanted to change them to fill horizontally (outside-in/inside-out depending on which one I put on the left and which on the right.)

Got the maintained window working perfectly, with a 1-pixel frame, and 1 pixel of blank space between each icon and between the icons and the frame. The problem I'm running into is that nothing I do seems to fix the effects window's 2-pixel between icons of blank space.

I tried setting each icon 1 pixel closer to the last (which should have made them end up right next to eachother with no blank space) but that didn't work. Checked for margin, padding, spacing, anything like that in the UIBuilder full attribute list, nothing. I'm at a loss. Any help would be greatly apreciated.