When I see sluugas that get some scrap to upgrade themselves, I think they look kind of... I don't know how to describe it, so I'm just going to say strange. Their helmets look like masks rather than a helmet with a gob underneath. I think a simple solution here would be just to make the helmets' color an iron-grey. However, if that's not an option, I'd recommend making the gob a bit bulkier and/or adding some horns to the side of the helmet.