Remember that both Coriolis and EDSY do not recognize the pre-engineered FSD SCO since INARA does not either (and I exported the build from INARA), I leave you a screenshot of the game (although it is in Spanish since it is my native language and it is easier for me to play in this one) where it clearly says "Prediseñado" (pre-designed or pre-engineered), this one is actually the 5A that I received for participating in the bombing of Cocijo, although I'm later acquired 4 more, so is not that I don't know the correct module XD.
Regarding the armor, thanks for the information. I didn't really know that since I'm not one to pay attention to all the statistics and what affects them. I actually thought it reduced it even more, but I never checked if it actually did. Without a doubt, I'll change it to heavy duty.
As for combat, I don't necessarily use it for combat, but I like to have my ships prepared for defense since I constantly maintain high notoriety (I'm not a criminal XD, but since I'm increasing combat rank by attacking settlements of rival powers and collecting Power Play data along the way, I rise my notoriety to 9 and get attack so many times that I'm paranoid now XD), I do have light modules for when I'm exclusively exploring.
And finally, I already had a maxed-out trusters with that modification, and I was too lazy to buy and max out a new one with dirty tuning. XD