Another ton for MLX! the cAP is basically a useless piece of shit when you use ECM. Now ECM sniper MLX get another ton for maybe DHS.
5x is probably too hot because the SCR is on the edge with 5 with 22DHS and the adder would have 16, but you will be able to do a better 4x MPL build having 1 empty arm, so once you drop a ST you are left with 3.
Could also run a combo of MPL and SPL for the Adder and have good enough cooling, with firepower enough to make it a threat. Not a perfect solution, but it can work.
Adder works very well with 4 MPL currently as that's my standard fit. Not actually sure what you could do with an extra ton - ERSL for when you lose an arm? Problem is even then you're moduled for MPL so a ERSL is.... not worth much.
Just had a look through my old fits and that extra half ton however will really help the SRM and SSRM builds as their main problem was always ammo for me.
I brought an adder to a lobby drop the other day and was very pleasantly surprised at how tanky it is with the leg and arm armor/structure/whatever buffs. Stood up to the enemy SSRM SCR for a lot longer than you'd expect.