Update: swapped my brass helmet for a fiberglass one on the 60 foot river job and my neck quit aching
Honestly, I dove a Mark V for the first six years and just figured the sore neck was part of the gig. Did a 3 week stint last spring on a pipeline crossing in Baton Rouge and a diver named Pete handed me his fiberglass hat on day two, said try this before you wreck a disc. The weight difference is nuts, my top side guy even said my hose pulls were smoother because I wasn't fighting the helmet. Anybody here made the switch and found the seals leak worse on the lightweight shells, cause that's my only gripe so far.