I do not recall having these gaps in version 3.4, I only noticed them with the Beta
What do I edit to get rid of this?
It's hard to say just from the screenshot. As previously noted, version 3.7 is running under a completely different browser/rendering engine, so there will likely be some differences in how the layout is rendered. That said, you might try removing the "Blank" cell to see if it helps, or any of those that aren't currently displayed (Stakes, Ante, Next Stakes, Next Ante), unless you actually use those at other times in your tournament. I'm guessing that even though those cells aren't displayed, there might be some space allocated for them, thus the empty space.