To master (100% FAoff + fixed weapons), I've already 95% mastered flying 100%FAoff, but I have yet to hone the last 5% of accuracy to land shots with fixed weapons with a lead time like rail guns for example.
An admirable goal indeed!
I did the same in 2017 and became one with the Plasma Accelerator.
Mastering that weapon added a ton of fun to combat for me, and modifying the Advanced version I bought in bulk from Patreus via PowerPlay was a really good decision as well.
TIP: Buy yourself a Type-10 and kit it out for combat, with a focus on dual fixed large hard points. (Belly Mounted) I find it a very "stable" platform for Dual Plasmas against medium to large high ranked (Threat Level 4) NPC ships. (Pythons, Condas, Corvettes, Cutters etc.)
Although I don't use RailGuns currently, I am sure the T-10 would be just as effective with those as Plasmas. At least when it comes to accuracy.