"Thom Stewart" wrote

Now on "Spitfire" they increased the height by using battens instead off
a gaff boom to decrease the heeling force and added another sail abaft
the other mast.

Sorry old chap, but on a tandem rig one mast is not abaft the other.
They are side by side.

As for battens increasing the height of the sails, you gotta be kidding.
The purpose of battens is to shape and flatten the sail and to
facilitate less twist in the leech.

CN