The bubbles werent coming out in the smaller holes...
What did you use to create the holes? (both the current larger ones, and the initial smaller ones that didn't work)
If you just used a needle or something to create the smaller holes, I imagine the tube self-sealed, so you might need to find a way to create small holes by actually removing material. maybe a tiny drill bit if you have one, or maybe by heating a needle/pin and melting a hole?
you may be able to wedge something (toothpick pieces, etc.) in the large holes to get the same effect, but it would look pretty ugly.