I lent my Chappel book out a few years ago and have not seen it since. And I can not remember the frame details. Salt box configuration?

Not sure why you would change the orientation but keep the same foot print? I am sure Steve put those plans out with thoughtful content. Will you be adding additional support under the now 22' tie beams? Have you added or take away a bent?

One aspect I notice with SC's timber sizes is the 7" width material, he is mill ruling with no housings. If you are scribing or mill ruling this will work, but if you are housing an inch or half inch then you will come across problems with tenons bottoming out against each other. I would suggest 8" widths for 1/2" housing and 9" widths for 1" housings.

Brace stock.... are you planning on cutting curves into the 3x8 brace stock? I have switched to 3x5 spruce brace stock if the brace length is under 50-15/16" long and 3x6 if over that, to a certain length, then up to 4" stock if bigger is required. I like the 3x5 brace stock as the brace pocket is much shorter than with material in the 8" range, it is a time savings/expense thing. Straight brace stock, btw, unless organic shapes are present in which I chuck out all time savings/expenses cause I have seen brace pockets up to 4' long.

Pegs... I am using mostly 3/4 hardwood pegs, What does SC suggest? Spruce has been seen used traditionally but usually in full inch sizes and up. Red oak, maple are a couple choices you should have, selected out of the finest fire wood. If you have any joints in true tension then they need to be sized accordingly, but most joints are in compression.