Checking gantry rail level for ROR

I’m in midst of observatory roof retrofit to ROR style and got gantry posts set today. Put 2x6 across span with digital level to ‘check my work’ (0.1 degree slope from N to S). I had compensated in redesign from original split-roof build by bumping south wall up by 1/2” in relation to north wall to offset pre-existing 0.5 degree slope from N to S. Worked out well since now down to 0.1 degree as gantry will be moving roof to west on rails using N & S walls as base for beams.