option one would help torsionaly in a turn, not to much in the longitudinal (tip to tail) direction.
i would be concerned with the stress concentrations where the wood stops.
If i were to do any reinforcing i would add carbon tape from the rear binding out to the swallow tips on the tail ( reverse V pattern )
I personally wouldnt be that worried about the tail flex. A normal tail of a board rolls up yours is now flat. Many boards have rocker in the tail and perform fine. My pow boards of choice is a lib snowmullet and k2 gyrator which both have rockered tails.
try it first, modify later. This board will ride different than others thats the point, adapt your riding style to fit the board.