Thanks Stormy!
I wasn't sure which cartomizer the other one was but it is definitely neat that the design will get along with longer ones. Presumably the Boge 510 was one of those 2 in the video.
I was pretty disappointed at first with the whole body being stainless steel, and do still wish it would be possible to see the juice through the side, but v4 still solves the main design flaw I saw that made me unwilling to buy a different tank - the tank coming off and juice leaking everywhere. Another bonus is we won't have to worry about whether any juice we put in it will crack or otherwise react with the tube.
As long as I know what size o-rings the v4 will need so I can replace them when it's time.
It would be neat if they were the same size as the ones for the v3.
Thanks,
Nic-holio