I really dont like ANY holes in a carbon tube, no matter how small and no matter the location.  I don't even like the setup of drilling the tube near the tip and putting screws in to hold it in place.  Over time, I dont care how small the hole, a crack can migrate and one can form small enough you dont even know it is there. 

I've never seen any problems with having the vacuum issue. 

Others have had success drilling holes in carbon tubes, I just personally don't like it. 

Just my .02

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