I hear your frustration. Just be patient and keep messing with it.
I also noticed an improvement in my shorty(sp2) after putting an O-ring on it. I just put it on the bottom cap & it stays there below the threading. I am using the Ultrafire 16340's.
A good test is putting it together without an atty/carto etc. Hold the SP2 vertical and then turn it upside down. Now that I have the O-ring on and have lubed it with Noalox the pin in the top will glide when I turn the PV upside down. This is without me pressing the button.
When you put the atty, or in my case the 801 Fusion carto on, it will prevent the pin from moving unless the button is pressed.
Another way to test it is to look and make sure that you can see/feel the pin move up when you press the button. I also make sure that the pin is flush with the threading something on the top cap. I currently use a combo of; 801 to 510 adapter with LR Carto's & the 801 Fustion Carto's from IkenVape.
IMO getting these to run smoothly is just a balancing game and getting to know your PV. Yes, it's frustrating...but I guess that's what you get when you essentially get 2 mods for $45