Neil -

Here in NNE I work EWP almost exclusively, and don't hesitate to draw it, Spruce either, and this typ with tenons cut to snaf thick.

Depending on your geo-locale timber will stabilize at somewhere around 10% a bit below your 17 to 20. Did your sticks work like they were fully seasoned ? Was the material removed dusty & dry ?

"We build too many walls and not enough bridges" - Isaac Newton

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