If I am reading this right, your 12cm lasers are a little bit overengineered, having capacitor 5. They only need 4 power to fully charge, so capacitor 4 is sufficient for maximum ROF. This would also lower the power requirement by 4.
The same goes for the 25cm. With capacitor 4 it will recharge in 20 seconds, same as with capacitor 5.
Another 4 power saved.
Currently you need 40 Power (which you have)
Each 12cm laser needs 5 power per 5-second-tic
Each 25cm laser needs 5 power per 5-second-tic.
As I said, each laser could be build with capacitor 4 for the same ROF, which would reduce your power requirement to 32 (and make the lasers a bit cheaper)
And yes, your main beam firecontrol should get a faster tracking speed. Assuming you have researched 3.000km/s beam tracking speed, a 1.25x size, 1.25 x speed would be sufficient, but if you increase the ships speed, you´ll need an even faster (Weapon tracking speed is either
The basic beam tracking speed you researched
or
The speed of the ship, the weapon is mounted on.
whichever is FASTER!
Oh, and I agree on the speed thing. My personal rule of thumb is one engine per 1.000t (i.e. 25% of total mass) for everything except for Brawlers (i.e. Beam armed ships), which get a couple of additional engines up to 35% of total mass.