Seems like a strange choice for a small agile viper though.
Well, not as much as you think. You could say:"Agile ships should use fixed, because they have higher DPS and aiming is easy when you are agile."
But you can also say:"With turrents I'll do damage 90% of the time, and I'll just focus on not getting hit myself. With fixed, my positions are limited to those within my arc, with turrets I can evade any which way and still do damage!"