Actually, you guys already have a Linked Dual Light Laser in the Dorsal position included with the ship. Adding one to the Ventral (bottom) will only cost 8,250 and 1 HP, not 11,000. Then you've got 2 turrets top/bottom. (Adding "linked" weapons costs 1/2 price and 0 HP for each addition emplacement; so Linked Dual Light Laser is 1.5 cost and 1HP. Replacing that is 0 HP, but the same cost calculations. Table 7-17 on p271, bottom row.)
However, at this price you might just want to install the Quad Laser Cannon for 8,000 and 1 HP in the ventral position. It's potentially 2x as powerful for the same price (and is Accurate, giving 1 boost die to every attack).
Also, I'd suggest instead of buying 2x smuggling compartments, use the extra storage mod once for 1,000 and will give you the same 50 encumbrance conversion for only 2,200 credits and 1HP instead of 2.
So by my math, that costs 8,000 + 6,400 + 2,200 = 16,600, leaving 5,400 for other upgrades. Aren't I nice? :D