To determine the effects of excess shield penetration.

The aim of the experiment was to determine the effects of shield penetration, specifically if excess shield penetration (Shield penetration higher than shield resistance) had any effect on damage. 2 frigates were pitted against each other, with the same type of weapons to that damage could be compared directly. 1 ship had 119hp, 3 frigate small beam lasers (Penetration 10) and a normal shield generator (Resistance 9).
The other had 2 of same lasers, 177hp and turbo shield (Resistance 7)

Damage per unit shield was 0.81 and 0.84 respectivly. Damage per unit hp was 2.81 and 2.83.

Results here 45% win rate for the frigate with 3 lasers. Variance is put down to extra damage in second frigate.

Conclusion: Excess shield penetration has no bearing on damage.

Id guess that in future there may be higer resistance shields or maybe the mechanic will change. As long as you are over 27, it doesnt matter what penetration you have.
The experiment was done by making 4 frigates attack a single other frigate. Win/Loss ratio recorded. All 4 of the 3laser frigates were on player side (I determined before hand that it doesnt matter which side you are on). Ships were stationary for most of the fight, though the more damaging one was twice as fast. Also had more modules, to give it more hitpoints. This could also means it has a better change of not getting a laser knocked out, so it could continue to deal full damage.

Well, at least now me know.