And I don't believe the stories of "my such and such atty with a long 510 sits flush". No, it doesn't, and it can't.
I can't speak for anyone but myself, but all of my tfv4s sit flush on there. Maybe the pin isn't as long as some other tanks, but I know a lot of people have said the tfv4 won't sit flush. Mine does. I have been using it for 6 or 7 months that way. It has sat flush the whole time. Fortunately, it hasn't given me any issues.
That said, the 510 is far from perfect. It SHOULD be deeper and able to handle a much longer pin. I feel that is the only downside to the mod. Truthfully, I think it was just a matter of form over function. They wanted to make the RX200 as small and cheap as they could, and this meant putting in a very short and subpar 510. While it will work fine for some, it doesn't work great for all. For me, it works fine since all I use are Griffin 25s and TFV4s. If it goes out, I still think it is a great mod that I will just replace the 510 with a higher quality one. Until then, I will keep using this one and have a spare one at the ready for when that time comes.


There are my pics to show that my TFV4 truly does sit flush on there.