A little more progress...
The cowling and hatch are basically complete, with the extra layer for the belly is being moulded ready to be glued on. Total weight of the fuselage, hatch and cowling as it stands is 13 ounces. There is a lot of excess in the cowling. I am guessing to some extent, but hope to have the complete, fitted out fuselage come in at about 1.5 pounds, and a total flying weight of about 5.5-6 pounds.
I have ordered a nice Tru-Turn spinner, opting for the basic international postage (us$12) rather than the international expedited (us$185). I would prefer to buy from a LHS, but the nearest supplier of any kind is 60km away, and the nearest suppliers with a good range are more than 400km away, so I order most stuff online.
I have included a picture indicating the concept of how the main hatch will work. The CF rods will go through the rear 2 hatch formers and into the front cockpit former to locate the hatch. The catch will be mounted on the front 2 formers, and engage with the firewall. It will be operated by inserting a suitable probe through the carburettor air scoop, giving a clean surface. The second catch is simply to show the mechanism.
I have also found a partial solution for the weather conditions, a misting fan. It sprays a mist of water into the draft from the fan, cooling it by about 5 degrees (or almost 10 degrees F).