Just to clarify, the theoretical 1" is just a theory. It will be pulled from the outside of the post and end up being more correctly measured as 7" from the reference face on your 8x8.

I don't see the 11" deep/long through mortice in the post being helped by making it shorter, you have already severed the fibers in the post, even if it was just a 2"x2", that may be a stretch but is shows the point.

Then there is the whole picture, span of building, roof pitch snow loads, species, peg size, spacing distance from shoulder, what day of the week, moon phases, etc. that can weigh in on this. That is what engineers do.

Where in Maine are you?