Here's an very very ruff exercise in futility.
(the deck tapers)
Excluding the stiffness factor of Deck as the web.
(obviously should be repaired as noted by previous posts)


Moment of Inertia = bh^3/12 + A*d^2

bh^3/12 is negligible.

So using I = A*d^2 for a 12" wide deck


Checking existing fibre glass at deck flange with an area of 1 in^2

I1 = 1.0 in^2 x (6 in)^2 x (1) = 36 in^4



Adding (2)0.125 in^2 of carbon in both sides of deck flanges from bow to stern.

I2 = 0.25 in^2 x (6 in)^2 x (29) = 261 in^4


I3 = 36 + 261 = 297 in^4



Proportional change in stiffness.

I3 / I1 = 297 / 36 = 8.25


For 1" of measured deflection PER hull delta becomes

1" / 8.25 = .12 in