If you show anythings, fire with double tape until he dies or overheat approche. So simple and effective.
With a LE and more armor & ammo (LE310 is also possible with original armor values and exchanging 1t of ammo for ½t) XL kingcrabs are usually too easily killed :O
I would argue that King Crabs has a very huge CT hitbox and you if you are facing someone, your targets really can't miss your CT. I heard multiple times my friends in my unit laughing about how easy is to hit and core the CT of a king crab and me too I still can't unterstand why I kept using it back in the days (4xUAC5)... TBH, it's the only mech I have ever sold and didn't bought back, despite being my personal best chassis regarding aesthetics. But now that I think about it, both side torsoes are very easy to hit too if someone is flanking you because you have the empty pods on your shoulders, plus many assault mechs now run with LE engine instead of a STD, so I guess many people will go for side torsoes instead of your big and bulkier CT... I guess that now with LE it really about picking your poison.
King Crab has a huge torso altogether. If you ever get into a match with lurms with an XL, you're fucked. Light Engine, slightly less so (but only slightly)