Ar 1/16" holes safe in an enclosure for a 1/4" sling?

I've got a bunch of slings coming on Friday so I'm rushing to get enclosures ready. I've never had slings before, only adults, so I feel like a noob. Anyway, I picked up some acrylic boxes from TAP plastics and soldered small holes in them. Pictured here are the 751, 754, and 760 in ascending size. The largest holes are about 1/16" though many are smaller. Are these safe for the slings? Will they be able to squeeze through?

I only have this picture of the finished boxes. I can post a close up photo later if necessary, I'm just not at home right now.
EDIT: Here is a close-up of one of the larger holes on the smallest boxes with a ruler for scale. Pretty sure I'm worrying over nothing, heh.

I read the TKG over the summer (library) but I ordered my own copy only recently. Amusingly enough it came tonight. From page 253 Stan says, "Ventilation can be provided with six to eight holes, less than one-sixteenth inch in diameter...."

I'll just superglue closed the ones I think might be too big.