LIGHTSHIP CORMORANT / LADY DIXON - Sails

Having had a sneak preview of a lightship dated 1907/8 (which I cannot share yet), I can, with the aid of a skilfully traced diagram reveal the set-up (Photo).

This shows the mizzen/lug/aft/whatever sail furled and there is no boom visible for the foot of the sail. So if all that had to be done is to unfurl the sail and hoist the head with the block and tackle that is visible there, then perhaps this sail looked something like this (Photo).

As the sail is not for propulsion, I assume that normal rules of mounting it do not apply.
Over to you experts.
David