I have a split level house built in the mid 1950’s which has 2×6 rafters 12 inches OC, and some have started to sag over a half vaulted ceiling area which has a relatively large span (~ 13 feet).  I want to give the rafters some additional support.  The rafters are connected to 2×6 rafter ties which also act as ceiling joists for the second floor.  These rafter ties are secured to a bearing wall which holds up the center of the house.  However the rafters are not directly supported on this bearing wall- the rafters are located ~ 16 inches above the bearing wall (6/12 roof pitch).  There is a very limited attic space above the 2nd floor, but there is insufficient clearance for a purlin in this area. (See attached pic).

So the first question is whether or not placing braces directly under the rafters attached to the bearing wall would provide additional support beyond that of the current rafter tie configuration.  If yes, the second question is whether a diagonal brace (Option A) or a vertical brace (Option B) would offer the best additional support (see attached pics).

Any opinions would be appreciated! Thanks in advance…