GrandGauss is a special bolt, and the Corvette already has a special mount, so why not just put it on the special mount? If you do that, then there's extra room on the Capship-Heavy mount. For that, I suggest hacking an icepick beam (although you said you wanted long range). The icepick beam has a rather unsatisfactory range (~4000 meters), but the damage is incredible (OVER 1.5 million mjs per second, that's more than 1 torpedo per second!). Have a good reactor, however. Icepick eats tons of energy.
If you don't want an icepick, try a LR_Pminus Mk IV beam or the like. They are really long ranged and do a lot of damage.
For comparison:
GrandGauss (aera): 40,500 damage, 35,100 phase damage (damage that goes straight through shields), 0.75 sec refire delay (1.25 shots per second), range 190 km
LR_Pminus Beam Mk IV (confed): 81,000 damage per second, no phase damage, 6 second beam stability, 2 second refire delay, range about 178 km
Icepick (rlaan): 1,620,000 damage per second, 1,620,000 phase damage per second, 2 second beam stability, 1 second refire delay, 4.75 km range
By the way, weapon hack method is same for Mac or Windows.
Oh, and if you want something that does a ridiculous amount of damage (54,000,000,000 mjs per shot) and are good at aiming horrendously slow missiles, use capship missiles
. Capmissile + capship = Giant nuclear explosion.