TIR + XM-L is OK, but all flood. If you like the beam from the Lux V (L2, L4, etc), go for it. But that's about as tight as the XM-L/TIR will focus. I have an XM-L'ed L1/Cree, and it's essentially a 1-cell L2.
I have put XMLs int a number of surefires. E2L E1L. All the LED surefires work fine. I have used the stock optic (it makes for an easier swap), but I prefer to replace the reflector in them as well because I like the look of it and it gives a nicer beam. Upgrading the driver is not a bad idea either if you gonna go to the trouble of opening the head.
BigC said that XML on 12.8 mm board fits extremely well in L1's head. You can actually use stock screws to tighten the star to the heatsink.
I would like to know if my LX2 is similar. Does someone has some pictures of seperated bezel?
Plus, is there any place other than illum.supply where you can buy XML's on 12mm mini stars? One german dealer offers warm white version (T3), but only as bare bare emitter or fitted on 20mm star. Could i use that one instead?