Also, in the talk DonP is mentioning the speaker told how he figured edge distances in the post with a housing. And I believe he didn't count the housing depth as a reduction in the post width. And in other words he figured the distance from the edge of the post as if it didn't have a housing at all. This added to the available distances for figuring out the placement.
I too remember hearing about not placing pegs too high in a wide tenon, and that they should be favored towards the lower side of the tenon.
So, in Thane's drawings, posted above, I'd delete the top peg and use two pegs offset in the post so that they aren't both in the same grain line.
As I remember one general rule of thumb for peg placement with 3/4" pegs through 1 1/2" tie beam tenons were 1 1/2" off the tenon's shoulder, with a 1/2" housing would make it 2" off the edge of the post. Two inches up from the bearing edge of the tenon to the first peg hole. And the second peg was up 2" from that and another 1 1/2" away from the shoulder, making it 3" from the edge of the timber.
