More method...................... sometimes I wonder why.
The rudders, doing this to both, at the same time.
First I make the cuts in the appropriate places, in the Rudder, not the vert stab.
Then like the ailerons a plastic strip for the hinge posts, .5mm card.
After I have inserted the card I mark the vert stab, hard to se but I did.
Then I make a slot for the hinge piece, on one side.
Then mate the fusey halves and transfer the slot to the other side.
Then trim the card to fit in the slots, top is narrower than the bottom in width.
Blimey, it Fits! ready for gluing in the slots at assembly, not until it's ready to go together.