Thought I'd finally stick my nose into this thread. After 6 months of vaping without having tried a single of the famous Kayfun family, I finally bowed to the inevitable a few weeks ago and bought the Infinite 1:1 clone from a UK vendor.
Liked it quite a lot, so a week ago I bought the "Improved" Infinite 1:1 clone from FastTech - the one that comes with the v4s adapter in the box, and has the single "striped" metal tank instead of the bell cap. And I really like that stripey tank. One thing I wasn't super keen on on my first Infinite was the three-part tank section with the nut, which seemed a bit cumbersome - and once or twice came undone when I was trying to adjust the JC.
I didn't want to use the bell cap and lose top fill, so the single-piece striped tank is a great compromise. Looks nice too!
The only issue I'm having now, with both, is the dreaded spring resistance problems. On one of them I've tried a method involving reversing the airflow screw and then tightening it from the top (through the airhole from the deck), just enough to make contact. That seems to be working OK in terms of resistance, but I now have huge problems opening the JC - I probably need to back the screw off just a fraction. And I haven't yet got the screw locked in one position, to do that I believe I need to punch an indent in the tube to hold the screw (or I suppose I could add a blob of solder.)
I did try my own solution involving a brass nut, trying to re-create the Steam Tuner's Spring Update. Unfortunately the nut is slightly too wide on the outside diameter and is shorting. I might be able to file it down a bit more, and plan to try that. It was also fractionally too short so I have to have a separate washer under it, also not ideal.
I'm sure there's hundreds of posts describing/fixing that issue in the thread so I'll do some searching to see what other solutions there are.
Anyway I'm enjoying my KF4s now I finally have them

It seemed crazily over-engineered to start with, but in practice I find it all works well. Besides which, using a single-piece tank reduces the number of pieces quite a bit. And I greatly appreciate any tank with top fill + accessible deck.