I have a sigelei V3 flattop. I like it and have had no problems with it at all. The 510 connection is slightly raised and there are no air channels cut into the top. Normally the raised 510 provides enough airflow for my cartotanks but not always. I always use cartotanks btw. I own a couple UDCT tanks that do not get good airflow because of their slightly sunken 510 connection. The UDCT sits flush on the top of my sigelei. I like the UDCT's a lot. The locking cartotank is great for my lifestyle. So, to fix this I plan on drilling an 1/8" hole in my sigelei. Just one should do it I believe. Right into the well around the connection. I have all the proper tools and skills to make it look factory so I'm not concerned about the looks. I'm concerned I'm overlooking something and I screw my mod up. Has anyone done this? How well did it work?