The ulliman web page shows a trace for shock loadings in G forces.
Ullman Range 2013 - Ullman Dynamics - (Version JPG) - Page n° 30 - Catalogue PDF | Documentation | Brochure de bateaux
See page 30.
It should be noted that the max G force experance by the Ribs is circa 12.5 G at Circa 45kn
Kenitic Energy is
KE = 0.5. M. Vel * vel
say mass is 1
then KE for the above mentioned graph is 0.5 *45*45 = 1012.5 units
for 23 kn the same boat has a KE of
KE = 0.5 *23*23 = 264.5 units or 26 % of the engergy of the boat at 45 kn.
It is a reasonable assumption that the Max G Force experance by that boat at 23 kn is 12.5 g *0.26 = 3.25 g
The max crusing speed of my boat is circa 23 kn (max speed circa 28-30 kn)
If I use the firgure of 3.25 G as max shock loading as a base figure for my boat at 23 kn. then the suspension seat must be able to support and deflect my weight of 90 kg by 3.25 G = 292.5 KG.