rocket mass heaters for tiny houses - any experienced builders in S.E. British Columbia or nearby?

HI everyone.

I am involved with a retreat center near Cranbrook, BC (which is an hour from the U.S. border near Idaho/Montana), which is looking to heat some 12' x 12 ' retreat cabins in the winter, where it can be -20C/ subzero F in the winter. The current mini-stoves need reloading every hour and a half at night which isn't practical for rentals.

I'd love to learn how to build rocket mass heaters myself, but not there yet - would need a lot of experimentation and guidance, although I love some of the designs I've seen here such as the Cyclone and others.

A challenging part is to know what size is practical for this space. The cabins are reasonably well insulated with windows that are perhaps 4 ft x ft

Any suggestions are most welcome!

Thanks

Geoff

There are several examples that have been built at Wheaton Labs, for example:
https://permies.com/t/71576/tiny-house-rocket-mass-heater
https://permies.com/t/62190/Peter-van-den-Berg-inch

These are in small spaces but still have thermal mass to retain that heat over a longer time frame, and might fit the bill.