FDL is a dedicated combat ship with awesome shields and a build should acknowledge that and work with those strengths, rather than diluting them.
Thermal bi-weaves with 4 resist boosters for most combat purposes. You could run prismatic for assassination jobs, but 9 times out of 10 the biweave's regen will far outweigh the extra MJ from the prismatics, even setting side the prismatic mass and power requirements.
Forget HRPs: You're in a shield tank.
Don't design for failure [shields dropping]; design for success. 4B SCBs are your friends [I like the 4 shots of over the 3 of Class A]. I use the Class 2 slot for another SCB, but go for cargo or whatever
You'll want an engineered 3-shot heat sink launcher to back those SCBs up. 2 for preference. Trigger 2 SCBs in tandem with each heat sink.
Over-charge your PP as little as possible, or you'll cook! Dirty A-class drives are of course desirable.
I tend to use the widely hated A Class sensors instead of D class when BHing or in a CZ, simply because the additional range speeds up the entire process of hunting and killing things.
A lot of weapons choice is preference, but I tend to use:
C4 gimballed overcharged MC with autoloader. I absolutely stand by that C4 mount being used for hull-wrecking weapons, rather than anti-shield weapons. Larger class weapons are much more effective against larger-hulled vessels. That's the way the mechanics work, and that dictates what goes in that Class 4 slot, to my mind. If you aren't running other MCs, then Corrosive is perhaps better than autoloader, as it will up the effectiveness of your other weapons.
Honourable mentions for C4 fixed cannon and PAs in that Huge slot. Lots of fun.
I used to run a pure gimballed MC load on th C2 slots: All overcharged, with 2 incendiary, 1 emissive, 1 corrosive. It's effective, but not really a combo that will improve your skills. Switching one out for a SCB busting railgun is good practice and satisfying. Moreso with an Imperial Hammer.
Another combo that I had a lot of fun with leaves 2 OC MCs in place [1 corrosive, 1 emissive], and mounts a pair of long range fixed beam lasers [1 with thermal vent]. There are few things more satisfying than popping a foe at 6km.
One thing that I should make clear is just how much time I spend overheating in a FDL. My knees are scorched from the flames jetting out of the dashboard! Managing the temperature is a trade-off for the sheer murderous power that hot-running modifications give you.
