JIB 4 DIMENSION !?

[TheThunderbird]

Hi everyone!
Boat is a Nauta 54' of Kaufman 1989.

Cutter rig, 23tonnes, in the sail plan I = 22m or 73'.
I got rid of 2furling gear, which I hate.

I plan for an Olympic jib 95%, staysail, yankee 65% storm jib (12sqm, 130sqft)

Question: I feel like I need a JIB 4 for some upwind (60degrees...) in heavy conditions, say F7-8, where the Yankee 65% is too large and less effective...

Some say size is 13.5% of I2 (squared) in so far a storm jib is anything between 3,5 to 5% of I2....but 40+sqm sounds too large to me

In said conditions, 23tonnes displ. 9Tonnes ballast, 8'draft... is there a formula to calculate how large a Jib4 can be?

I mean, the maximum bearable Upwind jib without mainsail, but NOT a storm jib yet...
Thanks