TimBeal - I would pare the end grain on tenon shoulders instead of trying to scoop out housings, being sure to keep bearing and mating surfaces flat and square to the layout, but essentially undercutting the shoulder or 'scooping out' as you say. Easier to do that than hollow out housings that do not come to the edge of the timber. This was slick work for me, prior to labeling and end sealing. Last step on nearly every tenon.
