The RSST will be perfect on an 8w. That's the one I first got for it. You can build a cotton micro for the RSST, as well, if you haven't already
The things to look for are adjustability, like the center pin, as you pointed out, the button location and ease of use, and conductivity. A floating center pin just means you can adjust it for varying atty pin lengths. The 8w has a double screw for this purpose. You just back out the larger screw, attach the top cap to the atty, then turn the larger screw in until it stops. This assures a proper connection. You can then unscrew the smaller screw to take out any battery slop. You have to do this iteratively, by taking the cap on and off, but it's quick and easy.
The 8w has an incredibly low voltage drop, making it hit as hard as the Nemesis or Poldiac. Other Sigeleis don't do as well.
IMO a kick sort of defeats the purpose of using a mech. They are for those that like the styling of a mech but prefer the convenience of a VV/VW. They will limit the amount of power you can apply to your coils, but they will also not be susceptible to changes from battery drainage.
can you do cotton micro for Agat2 as well are the any video's?

