In a previous post Brian Whatcott says...
If I say that a rough sawn 6 X 12 inch measures 6 X 12 inch, (duh)
and provide the Code approved results for such a beam, given the
Youngs and stress limit I specify, then I have provided an engineering
calculation which is explicitly correct.


Brian:

The calculation may be correct, but the answer is wrong. What is the
point of doing a calculation on a product that one cannot readily
purchase? That is not an "engineering" solution, but simply a
mathematical exercise.

What Rob is trying to tell you is that if you are going to make a
recommendation then base your recommendation on real lumbers sizes with
real lumber material properties. It does no one any good to specify
some material that cannot be purchased.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA