I like the diminished haunches. I've been working almost exclusively with scribe rule for a while now, and when I have to work with square rule, I feel like the reductions and housings are a pain. The haunches are not a problem, it makes no difference really whether you make a shoulder parallel to the face of the timber, or at an angle. The diminished haunch gives you more bearing on the end of a brace or the bottom of a beam. Without it, you just have the tenon supporting the load, no shoulder. In square rule, the housing is parallel, and you get the same effect on the bottom as the diminished haunch.

I will have to work on getting some pics loaded up so I can show you better how the layout is done. In scribe rule of course you have to do a full layout, and the mortises would have been cut first, and the brace or beam laid over the mortise, and the shoulder would be laid out by putting a square across the top and sighting down to the layout marks on the mortise. Hard to describe in print. Scribe rule is easier when doing it the first time, but scribing in new or repaired parts takes more time, and more test fits. I have pics somewhere of a new corner post that I had to scribe into a wall assembly, then flip it up on it's side and scribe it into the gable as well. Took a bit of time and not a good place for a mistake.

Member, Timber Framers Guild