I have been using cartotanks for quite a while now, and I use Boge cartos exclusively. I use 2 holes, one on each side. I punch them with a jig and carto punch I got from VaporAge, perfect holes, same size, every time. I diy my own juice, and it is usually 65%pg/35%vg.
After punching, I fill one of the condom ends about 12 drops or so, push the carto in, partially filling the carto from the bottom. Then it goes in my tank, and I fill the tank. I always blow it out to make sure the middle is clear and put it on my pv. I will draw on it without powering my pv until I can get a taste of the juice, and it's ready to go.
This works EVERY time, the only exception is if the carto or carto filling itself is defective, which happens very infrequently.