[Suicide Junkie]

The components by default have pretty good hitpoint values for a leaky armor mod.

All you really have to do is alter the armor.
Make armor 1 be 1kt, 20 hitpoints, armor 2 be 3kt 50 hitpoints, and armor 3 be 7kt 100 hitpoints.
And of course, remove the armor ability.

That'll give you a pretty good start. If you do the division, you will see that the higher level armors have fewer hitpoints, but during combat they will leak less often, and overall will be better.

For shields, try dividing their output by 10, their size by 4, and adding a crystalline ability with the same amount as their new shield generation amount. 20-30 physical hitpoints would be good for the leaky armor effect.

As for getting the % numbers, 50% = 1 shot hits the shields, 1 shot hits the armor, boosting shields back to their original strength. Overall every other shot hits, averaging 50%.
If the weapon does quarter to shields, you need to hit it 4 times to drop the shields that you created when you hit the hull. Five shots per cycle, 4 of which are blocked by the shields. 4/5 = 80%