Anthony,
Our boat insurance stipulates that if gas is installed the bottle has to be in a a container vented overboard! I think the "regulations" say that it should be enclosed and ventilated i.e. it needs to have air flow through the container with the air supply coming from outside near the top and the outlet at the bottom. The outlet must not be too near the waterline or it could flood the container and/or prevent any gas from venting. When I installed a gas locker (within the main cockpit locker) on my previous boat, I built an enclosed box in ply with glass fibre reinforced joints and a lid with rubber seal. The lid had a sealed inspection hole to allow the gas to be turned on/off at the bottle. I had an inlet through the topside and the lower outlet via the transom both via a hoses and skin fittings. In your case, I can see that using the fore-peak locker gives added issues but it should still be possible to do. I think Calor do a "leaflet" or maybe it's web based now, giving the best practice.
We use a portable gas burner with small gas cartridges. Not sure how we stand insurance wise but we declared it on the application. We also have a water tank in the forepeak so if we had a full gas installation this would be more added weight at the front of the boat. I think I would go for a "spirit" stove like Juicy Blue if we had to change.
Incidentally, has anyone devised a method of securing the "standard issue" portable stove?
Regards
Chris Cobb
235/48 "Tarakihi"