Look at the imgur link. You’ll just need to stabilize the copper tube by, perhaps wrapping cardboard around it to fill space in body tube.
My light now has an XH-P 50, a new FET driver (2S) and it is incredible... except for the part where the plastic reflector started to melt! It's 25mm deep x 40mm wide so a C8 Al reflector may fit. Since the reflector holds the MCPCB in place, I see the need to drill some screw holes to hold it down to ensure thermal conductivity. Does anyone here (in US) have a C8 reflector they'd like to get rid of?
I just bought the 4 AA model. This is not the older one with the reflector and the COB but just the reflector which is rated at 300 meters at 600 lumens. The light is all stainless which is quite heavy. This is a good choice for those who live near the ocean. The battery carrier is a bit fragile and not virtually indestructable. The tube is quite slick and I expect a lot of people will drop the carrier. I would be interested in a carrier with 4 half D batteries and a USB charging port. This is the best light I have had yet for use as a bicycle headlight. I am going to bolt it down to the front rack with conduit clamps and just remove the carrier for charging.