The run time tests were done with fresh out of the box SureFire CR123's. The head and pak are "E" series and Aleph compatible. The Light Engine though has different geometry than the XR can based light engines. The head and LE are not compatible with other heads and LE's on a sub component basis, to my knowledge.
It is not obvious in the picture above but this LE is similar to the Nichia 083 LE in the SunDrop in that the MCPCB stands slightly proud of the can with its top surface ~ .015" higher that the top faces of the can's castle points. As with the SunDrop head, the Haiku head also has a shoulder inside the head that the MCPCB gets pressed up against when the LE is tightened in place. This puts the MCPCB in compression between the can and head enhancing the thermal conductivity paths on both the top and bottom of the MCPCB.
The LE threads are already in tension within the head and this is an aid to thermal transfer. When the pak is screwed in tight in the head, the front lip of the pak is forced against the rear shoulder of the can and this contact surface is a good thermal path between LE and pak. The threads of the pak also provide a thermal path between it and the head.
Since both the MCPCB and the can are aluminum, they will expand when they heat up and this expansion should add to the comresssion and reduce the thermal resistance between them and the titanium even further. Titanium will not expand nearly as much as the aluminum. If for whatever reason the light is left on on high and picked up later on, holding it by the tail is much easier on your hand than grabbing it by the head. You cn work you hand up the light as you bleed off the excess heat with your hand.
When I assemble the Haiku head, I first install the LE and snug it tight in the head. I then push the 17-XR reflector down into the bore from the front until it seats around the Cree LED. The silicone O-ring around the reflector provides resistance between the head and reflector and holds it in place. I then install the window seal, window and finally the window retaining O-ring. The Haiku is straight forward in both assembly and disasembly and even the LE can be broken down into its constituent parts, should the need arise. The MCPCB is staked at for points within the confines of the can but it is possible to pry in and separate and lift the MCPCB up from the can. If you desolder the input leads from the contact PCB then the converter can be pulled out and free from the can. I stake the MCPCB in place so that the LE is held together and the MCPCB won't rotate as the LE is installed in the head. once installed, the staking is superfluous.