Hye Martin,
that is option 2.
But I think I go for option 1, this is stiffner itself I think and better sprayable for the customers own color.
Make 1 half tank with balsa with a horizontal centerline, glass and finish it completly.
Then make a plug of this (think with plaster).
this plug will be waxed several times, and then make the half tank.
Insert a few stiffners + mounting hardware.
Make the other half.
Put them together and finish the seam.
Wil do this also for the pylon.
And then one side is ready.
Sounds easy this way, now doing it
and thinking of a selling price
And make them for a Small L-39
Grt,
Berto.