Are you limited to certain sizes or lengths?

24' @ 10x10 is the maximum length / dimension my local sawmill can handle.

Have you read the TFG's joinery and design books (available on the website bookstore)?

Nope, but I just bought it as it appears to bet this forums go to book. Thanks for the recommendation. I added you as the referrer on the order.

Did you run beam calcs on all the pieces parts?

Sure did, based on the Code Type IV for timber frame houses in N. America. I continue to doubt myself though. Guess thats normal for a first time build.

Snow loads?

Not likely. I'm 60 miles S. of Atlanta, GA. The largest snow I've seen in my 33 years was 2 inches... and it closed the entire city. Couldn't find bread or milk anywhere

I haven't decided on a stair system yet. Id like to do spiral but I am confused on the code that would allow it to reach up into the loft (which isn't 7'8" high or 36" wide and therefore wouldn't fit code requirements). Still deciding. Its designed on the principal that I can just remove two of the common perlins in one of the sections that would satisfy two 36" landing (top and bottom) and suitable staircase. Then a ladder for the loft.

I'll be building on a large and modern crawlspace. One large septic tank header and vertical stacked 1st/2nd floor bathrooms right next to the kitchen to minimize drain piping and supply lines.

Could you elaborate more on the queen post and vertical header? This is the only design I can see that will allow for an open 2nd floor along with a small loft that also stays within the 26' height requirement I have to stay within. I am very open to ideas that would save timber and keep the 2nd floor with the loft!