Just had another thought. I don't have alot of experience using the "rubies", but believe the mortise is created in the adjoining timber.

Could the dimensions be added to the joinery in the ruby library, so when you picked a tenon for instance, not only would it be added to the end of a timber, but it's dimensions would come with it?

Or maybe as you suggested, timbers could come with a "reference edge" and "reference face" so that when you picked a timber, you also had to orientate it.

Anyway, because I don't know enough about these programs, just hoping those that do can come up with a "self dimensioning solution".

Thanks for your efforts and now I will shut up!