The peanut gallery weighs in with...
The solid flat tappet lifters. Id like to try out some with those nifty little EDM holes and see how they work out. I have seen some that weigh as little as 80 grams.
Hypothetically you could get away with lower spring pressures because of the lower mass.
Anything that I can do to reduce complexity and reciprocating mass in the engine without negatively impacting strength, hardness or toughness is a plus in my book.
Yes, I suspect that ductile iron rocker arms weigh a bit more than the stamped steel rocker arms. (I will try to bring a bunch in to work this week to weigh, and try to remember to post that data up). Buuuuuutttt... ill eat the increased mass on the rocker arms, and thicker rocker shafts to provide better stability.