All the weight (not a whole lot of it) goes to the to eave walls. At 12' your floor doesn't need a center support just some 2x10s or 2x12s, all 3 of the center screws aren't necessary - as long as you're doing joists and rafters.

They make marine boat woodstoves that would be perfect for a little space like that.

Just my opinion, you could lay down some solid CMU blocks and frame right on those. If the building moves its light enough to jack up with a car jack and shim.

I would consider framing the entire floor and subfloor with pressure treated. Insulate on top of the subfloor with 2"XPS. Anything underneath will turn into nest material for animals, I think.

I slept on it, and realized you probably mean just the center beam can changed, keeping all outer beams the same.  That would mean 8 foundation screws instead of 9, and only the center beam can have a larger size.  In reality, the perimeter is where all the weight should be, and the center screw will only really deal with floor bounciness...  I will do some more drawings today, thanks for the suggestion,

Quote from: 1akbig1bear on July 22, 2019, 11:45:09 PMWell we made our 2019 trip and hope you all enjoy the new photos
https://imgur.com/gallery/K3yyF5X word hurdle
Copy and paste and hope you like them

It looks great, I love this photo

Quote from: MountainDon on February 10, 2012, 08:03:32 PMIf you are doing a second story, IMO, the foundation should be located under the side walls, no cantilever. 2x8's would be too small for a 16 foot span on 16" centers. 2x10  #2 SYP or DougFir can span 16 feet,m 16" OC. For 18 ft, 2x12  #2  10" OC DougFir or SYP works.

Handy calculator here

Piers/girder are not prescriptive (code); if there are inspections in your area they may not be permitted. In any event if you use piers see this thread for what is a pretty good bracing system. Scroll down the page slightly from where the page opens.  Note Don_P's comment is Reply #83 further down the page.

Great idea, I'll try it out

Do you mean if ever I need to level the building?
6 screws would probably be sufficient, but I am a bit skeptical of the 5000 lb claim of the foundation screws.  
My thinking was that the center one would be the fixed one that is never adjusted, and I would use all the surrounding screws for the adjustment, thereby removing the need to crawl under (it is a grid of 3x3, 8 are on the perimeter with only one in the center.  I would also have to beef up the main beams to support a 12' span instead of only 6.  Do you think my logic is flawed there?  It is definitely not too late to change the plans.

Is it possible to change the design to use foundation screws along the two eve sides with no central ones? That's just my preference for minimizing how much crawling under the building I might need to do in future years.

Quote from: OlJarhead on March 15, 2023, 06:24:43 PMI also read somewhere not to store them at 100% SoC.

I believe the voltage for a planned storage period with LiFePO4 should be 3.3 to 3.4 volts per cell.

Interesting!  I always learn here

The controllers on the batteries only show DC Volts and Amps so it's hard to know where they are.  Currently they show 26.7v and I have a charger which is set to charge at 28v I believe (need to double check that).

I know the shut off is set between 20-21v so I can assume that's 100%DoD but was hoping they would have some kind of ramp that would give me an idea of where they are now.

I was told not to store them more than 3 months without charging them but I also read somewhere not to store them at 100% SoC.

Quote from: OlJarhead on March 15, 2023, 04:42:09 PMOne thing I need to find is a voltage guide to SOC levels for LiPo....anyone have a good source?

Rather than referring to these as LiPo I believe you should be using the term  LiFePO4, as LiPo can refer to a type that has a nominal voltage of 3.7 volts and is not the same chemistry as LiFePO4.

I understand SOC to mean "state of charge", correct?  Voltage is not a very good guide to SOC for any lithium-based rechargeable cells and batteries unless a very accurate voltage meter is used. They do not drop voltage as much as lead acid. Being off by 0.1 volt makes a bigger difference than with lead-acid cells and batteries.

I've seen a few tables but I can't say one is better than any other. I don't know where the data is coming from as they mostly all seem to have the same anomalies that I figure are coming from rounding off voltages to a tenth of a volt.

One thing I need to find is a voltage guide to SOC levels for LiPo....anyone have a good source?