While waiting for the Fafnir, you should use the mauler with the best quirks for ballistic cooldown (-10%) and laser heat generation (-10%). Shield with your arms and use your medium lasers to shoot down UAVs and/or apply some extra damage. Skilling into coolrun and heat containment is not mandatory but is kind of recommended, maybe a couple of nodes will be fine since this mech has already good quirks. Don't forget to max out ballistic ammo: you will have 54 rounds (27 alfa strikes) for a total of 1350 potential damage or 810 damage if the target is around 500 meter (non-Heavy-Gauss range) You can also adjust engine size / remove TC1 / ammo and fit some armor.