My A7s (i have a few) came as bottom feeders - there are air holes above the 510 threading and none in the topcap. They were some of the first RBAs i used on bottom fed mods.
You can also sometimes negate that wobbly centre pin by screwing it in clockwise as far as it'll go. I always did that and never had any issues with it.
My RM2s superceded them, and for fun yesterday i whacked a ropey old 26g dual coil macro setup in my igo-w4 to try! Not baaaad! 0.4Ω.
Air holes need to be bigger though.
T
You can also sometimes negate that wobbly centre pin by screwing it in clockwise as far as it'll go. I always did that and never had any issues with it.
My RM2s superceded them, and for fun yesterday i whacked a ropey old 26g dual coil macro setup in my igo-w4 to try! Not baaaad! 0.4Ω.
Air holes need to be bigger though.
T