91.531 (3) A comuter Category airplane, except that a person may operate notwithstanding (a)(1) of this section, that has a passenger seating configuration, excluding pilot seats, of nin or less without a pilot designated SIC.....yada yada yada
so i'm not sure if installing the jump seat counts as a pilot seat or not, if not i would think the aircraft, since the 350 is a comuter category aircraft now requires an SIC according to the above reg. since it has more than nine seats