At first I thought I should add some phrases concerning a good heatsink, maybe modding the upper part of the host and so on.. then I noticed that the posters name was scaru. :D
The full mechanical specifications can be found in the original post, but the height is 15.4mm. I always assume a little slop due to manufacturing tolerances and leave 16mm of clearance.
PPtk
Edit: Without optics, the tallest thing on the circuit board is the Inductor. Without optic the total height is 0.4mm (circuit board) + 5mm (Inductor) = 5.4mm.
The XM-L emitters are 3.02mm tall, so the height of the emitters is 0.4mm + 3.02mm = 3.42mm
Those numbers are a LITTLE low since there is some solder between the inductor/emitters and the circuit board, but at most the solder accounts for an additional 0.127mm (5 mil solder stencil).
For those who are intending on purchasing a DIY Kit, here is the assembly drawing - shows which part goes where. All of this information is on the Silk-Screen of the board, but I find it much easier to build when I can look at a reference (and possibly even make notes on it).
Gold plating for solder pads can be a bad thing! Gold tends to form intermetallic compounds with lead/tin/aluminum (google "purple plague" for a well known example). These can be brittle and poorly conductive. Components have been known to fall of circuit boards...