Quick PSA -
To keep things fair, straightforward, as-rules-designed, and minimize Modeling for Advantage, all hull-mounted weapons (that's to say, ones that are limited to a 45-degree fire arc by rule) should be arc-determined perpendicular to the flight stand, parallel to the table. So, the angle at which you've modeled your hull mounted weapon will be more or less irrelevant to its arc of fire.
When in doubt, in order to measure arc of fire accurately and effectively, take any handy piece of paper, and fold it evenly along one of its 90 degree corners ... now you have a 45 degree arc to use for determining arcs of fire from the weapon.
Several quick PSA posts incoming over the next few days.
We're closing in on NOVA at this point ... things are getting crazy!