I've been thinking about getting a carto punch, too. But I look at the two holes on my Altsmoke and Smoktech cartos and have had minor issues with them flooding. I actually prefer the one-hole laser-punched cartos, my juice isn't that viscous.
But then I see my friend's homemade punched carto and it looks... freaking huge. I am worried about flooding too many cartos. He says they are just fine, but I'm still a nervous nelly.