Reduce gap between listing cards in grid view

[morebrownies]

Currently, the grid view of listings cards gets very stretchy between listings:

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Ideally, the space between listing cards would never change. Instead, the gaps on the left and right side would increase in size:

[morebrownies]

Another example at a different resolution

[hoffmabc]

I know this is preferred but i'm having trouble making this happen with flexbox. I'll keep trying.