Ships & Modules

I know there is more of a bonus from Navy modules, but why do some fits include two T2 modules, and two Navy modules of the same type? Don't the stacking penalties still count?

For example, in some Tengu fits, people will have two Ballistic Control System II s, and then another two Caldari Navy Ballistic Control Systems. Is this to negate the stacking penalties, or do stacking penalties not count with Navy modules?

There are any number of reasons you might see this. Some faction mods have equivalent and/or higher bonuses while, in many cases, reduced skill, cpu and pg requirements. Could be that, this particular fit benefitted from CN BCUs and the pilot just hasn't gotten around to fitting 2 more or it could easily be that's what they had laying around.

for pve there isn't really much else to put in those slots that can do anything to boost efficiency. 4 or even 5 damage mods are somewhat standard. the 5th mod is typically a t2 damage rig as they give bigger bonuses than damage mods and will give a ~5% dps increase, a 5th BCU would be almost completely wasted.

the 2/2 or 3/1 style fittings are typically either to save cost or fitting. most damage mods have gotten pricey at 50mil I don't really mind fitting four, but at 100m I'd rather fit two or three. And I'm pretty sure someone else said it, but faction damage mods typically use way less CPU making them an easy option to get some fits to work. I have one fit where 2x t2 maxes out the cpu and I have to fit nanos in the last few slots, if I swapped to faction damage mods I could get 3 on.

Chainsaw, missile guidance enhancer. Heavy missile application is still not where I remember it

I get that. To be honest, I don't fly those as much as the regular ships and I am still at the figuring those out phase. Just finished the last Legion subsystem maybe 8 weeks ago.

Check the FITTING of both modules and you will understand...

Your numbers are off but the idea is about right. The first T2 BCU adds a total of 22.91% more DPS. The second takes that to a total of a 47.37% increase (that is, you get a slightly increased amount of absolute gain from the second damage mod despite stacking penalty). A third T2 BCU gets you up to a 66.63% increase from no mods (so still not bad; almost a third more on the third mod). The fourth T2 BCU gets you to a total of 77.43% over base -- and now we're seeing actual stacking really set in.

So let's get those numbers gathered in a readable form. For T2 BCUs, the increase from base damage is as follows:

1: 22.91%
2: 47.37%
3: 66.63%
4: 77.43%

Same list, but now we're using CN BCUs:

1: 25.70%
2: 53.77%
3: 76.32% (notice here that three CN BCUs performs about as well as four T2 BCUs)
4: 89.14%

Now since it's the actual topic at hand, here are the increases from 2 CN and then 2 T2:

1: 25.70%
2: 53.77%
3: 74.36%
4: 85.94%

This third option costs half what the second one does (more or less) and still does significantly better than straight T2.

Of course to really do it right what you want is a T2 ROF rig. Assuming the final layout adding a rig on top now gives:

1: 45.85%
2: 72.75%
3: 95.78%
4: 98.21%

At that point it's fairly clear that the fourth damage mod is a bit of a waste either way.

(Please note that numbers do not include reload time. RoF stats obviously increase how often you have to reload and don't quite give the paper increase you're looking at. But between reloads... well.)