I just finished drilling & tapping for the larger 2/8-16 bolt. Bolt seems to be holding fine, same torque as other 5/16-18 bolts.

Update : upon inspection, the bulkhead is centered on the beam location, so the bolts located front and aft of the beam would be clear of the bulkhead, if I cut into boat to fix from inside. However, if bolt inside the beam was stripped, I would be out of luck.