hi laura,
interesting that we both separate "ON" into mental and physical. i haven't tried COMTAN, with my IR/CR l-d0pa combo, i'd say i'm physically on - can drive a car, ride a bike, type - as long as i take my l-d0pa on schedule.
like you, i often get mental funks in the afternoon where l-dopa just doesn't help.
the "funk" manifests itself mainly thru trouble getting my thoughts out. so hard to measure that in terms of 'ON", i'd estimate i'm mentally off a little bit most of the day. i admit kind of a vague reply.