On the gable it will be necessary to splice the asfaboard vertically, should cross battens and a batten along the sloped roof then be installed to nail the short sides against? I haven't seen this on other construction drawings, but I think the asfaboard seems a bit too soft to have a loose edge. Even if you splice the cross joint with wind-proofing paper and asphalt adhesive as I read in a thread...
By the way, can the asfa layer be reinforced? I've had a few knocks here and there so the asfa layer looks a bit worn, it would feel good to brush on something bituminized.