Just to follow up on my earlier comment about Trenching cuts, I've just had occasion to trim a tenon shoulder - 14mm deep. Rather than use the shoulder plane I thought I'd try my Bosch Axial saw. Slid the metal plate across near the saw arm pivot and adjusted the screw that bears on it, so that the saw blade would just skim the tenon (top of which is c.28mm above the saw platform). I needed around just under 1mm shaving, so not even the saw blade's kerf width.
Put some scrap against the fence (so that the bottom of the blade would reach the full tenon width) then the rail with tenon, slid (glided?) the saw out, started it and pushed the saw across the tenon. No blade deflection and resulted in a very clean straight edge where the <1mm was 'shaved' away. Much quicker and just as clean cut as using the shoulder plane.
Based on that I believe that cutting trenches would be straightforward.