So, the opening of the catch cup on the Grand is 15mm diam. Basically, any atty that is < 15mm and can be somehow modified to allow juice up somewhere will work. The 510 extender/adapter works; but having two threaded joints operated by the same twisting motion can mess up a mod's 510 female over time (if you're gentle). What was the drill bit size? . . . . . . . hmmmmmmm, I believe it was a #56. Around 1.1-1.2mm should work nicely. I love the RM2. It can produce a very warm vape when set up with a micro-coil. All the heat stays in the vape, not the atty. And liquid draining back down almost instantly works very well for fully saturating your wick, but not cooking the juice you're gonna vape in a few minutes. When I squonk the RM2 (or any RBA that lets the juice drain back out/down), I hold my squeeze for about a three count. It takes a second for the juice to well up inside the atty. Then, when I let go, all that's left in there is a nice wet wick and a coil. Anyway, blah blah on I go.
