From what I've heard, don't pull the pop rivet until the shaft snaps. Just compress it enough to hold it in place, then punch the shaft out the back. That'll leave more "meat" for the tubing to push onto.
However...I didn't do that. I pulled the things until they snapped just like any other pop rivet. I punched out the shaft then pushed tubing onto 'em and RTV'd around 'em. Worked. It has been 950+ hours of flying and no static issues. I've passed IFR checks twice so far. As cheesy as it may seem to do it the "stock" way, it's hard to debate that it works and Van's pop rivet static ports don't produce as much error as other approaches have reportedly produced.