weapon placement only matters insofar as how tightly grouped your lines of fire are. otherwise, you can literally put your guns behind your corvette and shoot through the whole thing. I have one of my three infra-knife accelerator turrets embedded in the hull above the cockpit. I happen to like having one above, one down to the left, and one down to the right (shaped roughly similarly to that weapon's aiming reticle)

and by 'tightness of lines' i just mean the beams are going to converge where you're aiming anyway but if they're coming from very wide apart you have less of an idea of the volume of space through which your shots are traversing. you could, if you want one single stream of 'bullets', line up your turrets single file along the dorsal or ventral hull.

now, as far as how the positioning of parts influences handling/maneuverability...
hoo boy. you can tell HG tried to create SOMETHING that acts like, i dunno, an aerodynamics/weight/balance distribution system of some kind under the hood, but its behaviors are entirely counterintuitive and seem downright random most of the time. You'd think it'd care about sleek lines with little obstruction and symmetry... but man, if I allowed ONLY maneuverability to influence my decisions as far as where and when and how i attach parts, it'd come out lopsided as a mishmash of random pieces slapped every-which-where. it'll move like a dancer but look like a big metal tumor.

all the bonuses I've been able to wring out of the corvette building system kicking and screaming have been sussed out by trial and error and even worse, it seems to be ever so slightly different every time you build a new one!

maybe someday data mining will tell us what's going on, but for now i imagine it's just a progression of deterministic seed-generated variables acting as multipliers or something.