It's a little boost driver (it'll run the LED just fine from a single 1.2v NiMh), I don't think the boost driver's performance is dependent on the FET like a linear/DD one is.
I don't know for sure if that R200 is a limiting resistor, or a sense resistor. Either way, tweaking it should also tweak the output.
Disregard that part - I checked the o-ring and it's thinner than I thought, it's 1mm already. You could omit the o-ring and glue the lens into the bezel with clear silicone and get most of the room you need to fit a thicker MCPCB. Still might require a bit of sanding on the bottom of the copper board.
Spacer will end up somewhere around .200"-.210".
Plan is to bend the shelf in the pill upwards a bit, then press in the spacer to force it back down flat. And then rivet the whole mess together with the .250"OD copper tube through the middle.
Is that a spacer from MTNElectronics?
Nope, 3/4" 6061 bar stock. http://www.ebay.com/itm/360670546100
WHY is there no 18650 version of this light?? :~
I thought the answer to this was simple. Because you haven't built it yet. I'm really looking forward as usual to see how it turns out. Cheers. 
Pfff, you know I don't do things from scratch. Besides it sure seems like they were planning to do a whole line of 'Z' series lights, did the CR123 Z1, the AA Z2, and then... just gave up. Do you realize how many they would sell?
The step on the spacer is .010" taller than the recess in the pill, to make sure it makes full contact with the shelf and not the upper face of the pill.
There's a lot of stuff I'm not sure of, but one thing I know without a doubt is that spacer's not coming out of there without destroying either the pill or the spacer or maybe both. Good thing the threads were loose to start with, otherwise it would probably not fit afterwards. The press fit was around .006-.007" so it's now quite a bit bigger at the threads.
The SolarForce T1. Though I’d like to see a Z series 18650 light as well. Great mod work BTW.
Still need to shave down the top of the spacer so that the head bottoms out juuuust when the o-ring is squashed the right amount, and install the copper rivet-tube thing.
Cool show, I like this channel.
Wow comfy. That’s some nice polishing there.
Fine, I’m in for one. Also I’m stupid envious of all that you’ve done in this thread.
Oh my goodness man, what do you use to polish this baby this buttery smooth. Mothers mag and aluminum polish? HFT stick polish? I need to know with what and how! Amazing.
Yep, well, Eagle One mag/aluminum polish (it's just jewelers' rouge) first on plain printer paper with a little paste smeared on, then a final light polish with a tiny bit of paste on cotton cloth. I go straight from wet sanding on 600 grit just to get it flat and then right to the polish, all that crazy mess with multiple grits before polishing is just wasted time, the end product is exactly the same.
Put me down for 1 in the group buy 
Thanks. Now I know the secret to get an amazing mirror finish. I tried using mothers mag polish on a light, with a cotton dremel pad and I swear it looks nothing like the mirror finish you created. 600 grit is the key I see!
A triple in a light this small? I thought the Z1 was bright in stock form, I honestly never thought I would see a light this small pushing this many lumens. You are doing great things for this hobby. Please do us all a favor and sell us one of these.