This question comes up from time to time. Maybe try using the search function.
A regular here, I think it was Southace, maybe it was Morning Bird had a similar problem. I'm sure they will be along shortly with an answer. Failing that, I agree with HG
Eian and I are near neighbours (both live north side of Sydney) and have been trying to solve this issue for a couple of years now. As it turns out Eian might have found a solution today, a few days after I fitted a metho stove to Morning Bird. However, their are still a few issues to work through so the solution couldn't have been implemented in time for me to use CNG for Lord Howe in less than two weeks. It looks like I might have a choice of metho or CNG in the future.