I figured that when readying to rapid-fire, a whole row of photons could be loaded up in the bay, end to end.
There is no indication the refit / movie Enterprise ever had an aft (torpedo?) launcher
Whenever someone would mention the lack of an aft torpedo launcher on the classic movie Enterprise, I always said that had extra ones ever been needed, a hatch would open somewhere on the hull revealing a tube beneath. And it happened in the last movie!