OK. I do see why folks want to sub-ohm a rebuildable. It behaves different.
The RM2 came today (thanks for the super fast shipping, Rob! That was cool). I finally found a minute to have a go with it just now. I don't have all the other stuff I ordered (wire gizmo, cotton, etc) but I did have some silica I bought with my still-unused RM1 and a little half-threaded half-smooth machine screw loose on my desk, so I just guessed at how much 28ga to cut and guessed at # of wraps on a ~2mm screw (I guessed 12). When the coil was installed and the ends trimmed, it was exactly 1.5 ohms. That's what I was looking for, so I was pleased with my uneducated guess being right.
After metering, I put it on the 14500 mini and the coil glowed right up. So far so good.
I only really had two challenges. One was the little bitty holes in the posts and getting the coil legs (? right word, "legs"?) inserted because even with my readers, my old eyes were none too happy with that chore. - And the other was figuring out how to get 3mm silica through a 2mm hole, but when I failed at fishing it through with a piece of wire, I realized I should just line up the twists in the silica with the twists in the coil and pretend the coil was helicoil. That worked slick - really easy. Just screw it in and trim off the ends.
I put it on the the mini and squonked up some juice and watched the wick soak it right up. Again - so far so good. I pushed the button and watched it make vapor... so far so good. I screwed the top on and went to have my first RM2 vape... and it was less than stellar. So... huh. OK. I put it on my VVW which was set around 3.5v for the 1.5 ohm 306 that had been on it... and again, less than stellar. I spun off the RM2 and checked my ohms with a different meter. 1.5. I put it back on and gave it ~4.4v, and there was the cloud I was expecting. 12W is quite a lot higher than I've been vaping for quite a while... but this sure doesn't feel or taste like 12W. From a 306, i06, or a cisco aero, 12W would normally make the juice I'm using not so very palatable. It tastes pretty good right where I'm at with the RM2... though I suppose some fine tuning will happen in the morning.
So, my immediate conclusion is that this sort of rebuildable behaves a lot different than any of the attys I'd normally use. I can easily see why folks want to make sub ohm coils for their mechanicals... and why those same folks are so concerned about their voltage drop. To get to the exact same production I have right now, it would require 3.5v after drop and a 1.0 ohm coil... so ~.9 or whatever it is that's popular seems pretty reasonable.