I have a dual regulator that with an adapter can be used with either Camping Gaz Butane or Calor Butane & Propane. The withdrawal of the 3.9 Propane is an issue for the 405 as the 6KG cylinders will not fit. They’re about 2cm too tall.
1) Go the Camping Gaz route. Not ideal as Butane doesn’t work well in very cold weather and we use the boat year round, Plus, it’s significantly more expensive.
2) Transfer Propane from a larger still active sized Propane cylinder. Potentially dangerous but cost effective long term as long as you’re still alive to benefit:-)
I’m not condoning option 2, but Calor has put an awful lot of people in a tricky spot and it is likely that a significant number of people will chose this route. Should they do so I’d like to hope they do it away from the Marina.