As mentioned above, last item was to deal with humidification. I decided on a Honeywell unit which evaporates tap water through a wicking element using a squirrel cage blower. Noise level is comfortable. Just a soft whoosh. The previous Vicks steam unit required distilled water and was OK given the propane produced water. The new heater vents combustion to the outside causing RHI to plummet to 18%. Tough on skin, sinuses and delicate electronics (static).
The Honeywell unit keeps RHI around 45% which is fine. It also has a humidistat and holds 5 gallons in twin tanks. Seems good for about 24 hours. I don't have tap water in the shop so it's a manual fill from the kitchen sink.
Honeywell humidifier HCM-6009
Always helps mix up the air and reduce temperature gradients.
The Honeywell's wicking element will certainly accumulate calcium salts over time. We're on city water here which is reasonably soft out of the tap. Not sure yet what the wicking element's life expectancy will be. They are around $15. Distilled water is $1/gallon and I'd go through $30 a month. So I'm thinking this new system will be less expensive to operate. The fan uses less power than the heating element too. Certainly more convenient by not having to schlep in gallon jugs of water from the store.
We haven't seen single digit temps yet so I don't know how all this will handle that. No concerns, however, at this point. I'm expecting cold weather just means longer heat cycles and more water. Cost data to follow after the first gas bill arrives.