Because clanner mech can't fire 3xLPL without ghostheat, your own LPL have shorter range and clanners doesn't have the tech (at least yet) for the Heavy Gauss, so you need to hugh both to comfort them and to fully apply your damage. Jokes aside, with this build you are trying to have a nice pin-point mid-short range brawler, with the stopping power of a 2xGauss - 5xERML build Mauler but the same speed and way better tank. And before going on, you are NOT a brawler. This build is meant to be effective in those maps where range could be an issue but you will likely have the chance to get closer or the chance to fire a couple of shots before being enough close for your LPL to be effective and your HGauss to apply most of its damage (it does deal the same as a standard Gauss at lesser than 450-500 meters). You can fully take advantage of the laser quirks and they also have the nice addition of pinpoint damage thanks to the Hgauss: just remember to ALWAYS fire your LPL before the Hgauss, otherwise you are gonna spread your damage. This build is kinda hot: you must focus the right components and you should not fire untill you are sure to hit the intended component / target. Since you can fire very quickly your LPL, you can both torso twist between the shots or face tank if your target is fitted with weapons that will likely spread their damage (but it is hardly the case, since you are huge and slow). Skill wise, I would go for firepower (heatgen and range, cooldown is a nice addition, ballistic ammo is a nice addition too so you will have 6 or 7 ammo per ton instead of 5... From 20 to 24 or even 28), mobility (left branch, torso speed / yaw and maybe speed tweak, but that's probably not worth it), obviously survival, because your defensive quirks will stack with these nodes, every coolrun-heat containment in operations and finally coolshots and air strikes. ALTs: you can actually play a lot by removing a single DHS, shave/add some armor or downgrading your engine. The usefull things that you can add are an AMS for increased survivability VS missiles and a TC1 for a slight bonus range to LPL and a little speed bonus to your HGauss. This would be my alt.
