Slot-size on Laser-cut PALS.

I'm debating what kind of slots I'd like to use on my Laser-cut PALS, and I'm leaning towards slots that are 30 mm wide and that consist of only a slit.

Another option would be to make them 0,5 - 2,5 mm high, but I feel like the bigger the slots get, the more loose the attached item will sit, no?

What's the best balance between ease of weaving and tight fit?