Okay, here we go:
There's another benefit to having more hull points, and it's armor state. See that percentage of your hull? It doesn't only display your remaining health, it also displays the state of your armor. At 100% hull, your armor protects internals well. If your hull drops lower, your armor is damaged and it's easier to penetrate it, thus making more module damage.
Internal modules are protected by armor. Resistance applies here, I think.
External modules are not. The only way to protect your external modules (guns, utilities, engines and cockpit) is to angle your ship well, to use point defence/ecm/chaff/stealth or to install armor mods (sturdy weapons, armored powerplant, streghtened drives).
B-rated modules have more base armor than A-rated. On the Anaconda, I try to get B-rated powerplant if possible even on non-hulltank builds because it's positioned in front and is very exposed.
Now, selene jean and her mods:
First, basic bulkhead upgrades.
Each ship has default amount of hull, default armor hardness and default resistances.
Every hull is weaker against kinetic weaponry but well protected against thermal. Lasers also have very bad armor penetration.
Cannons have the best armor penetration and are overall the best weapons for sniping specific modules of large ships.
Lightweight hulls are the basic thing.
Military increases the base hull amount and resistance against all damage.
Reactive increases hull amount aswell, and adds even more kinetic protection, however thermal protection is worse. Mirrored does the opposite to your resistances.
Now, Selene Jean's mods for bulkheads can increase the bulkhead armor and resistances.
Hull reinforcement upgrades can increase the hull bonus of each HRP separately, their resistance bonuses, but there's also a chance that they will increase your armor hardness.
Those all stack together. Armor and resistances of bulkheads are combined together with hull reinforcements. My Anaconda has total of around 60% resistance against all types of damage, as well as hull boosted from 3000 to 5000. I tried turning my shield off and attacking Deadly/Elite Anacondas, they usually do 4-6% hull damage and 2-5% powerplant damage before they die.
Bulkheads themselves are not that important, it's just one module. Stacking resistances is the best rhing you can do - so, put heavy duty mods on hull reinforcements and bulkheads. Make sure to get the best overall resistances (you can't go over 75%, and going over 60% is harder because dimishing returns apply).
TL;DR: if you want to make your hull really powerful, install military bulkheads and several hull reinforcements (4-5 is good), and put heavy duty G5 mod on everything. Add some point defence for module protection (2 for big ships, 1 for smaller), make sure they're covering the same zone as your weapons (for example, Corvette's huge hardpoints are on top, and you need to keep your enemy slightly above, so put your point defence turrets on upper slots). Chaff helps a lot, stealth doesn't work in PVE at all.
If you spot a mistake in my post, alert me.
