I got the light bodies back last week and thought I'd share my thoughts. I sent off a 6p LED body and a 9p incandescent body (I think the LED and non-LED bodies are interchangeable, but in case it matters to someone). I also ordered the delrin bushings to allow you to use the smaller CR123 batteries the lights originally ran off of without any rattling.

I've worked with both lights in 27 degree weather and let them warm up past 100 degrees and at all temps the batteries fit perfect by themselves or along with the spacers. No rattles or sticking with either my 18650s or the CR123 & bushings. All the tolerances are perfect. I love it. Couldn't be happier.
I'll try to update as I test fitment with other cells.

I've tried the following 18650's
Ultrafire Silver 2400 mAh
Ultrafire Blue 2400 mAh
Ultrafire Green 2600 mAh

The Following CR123a's
Surefire Red Cells
Rayovac Silver Blue
Tenergy RCR123a 3.0v 900mAh Rechargable