Best explanation I've seen so far for Hemi cam/lifter failures

I was searching on rock auto for the pump, seems that Melling makes the crank gear that you have to use with their high volume pump. Does not look like the splines extend, just the face to where the balancer squashes the crank gear.
I was just wondering if anyone just runs straight weight oil in these things. I mean 5 or 10w oil is the cold point when they are running and it goes to 30 or 40 when its hot and that is where they are losing oil pressure. Not an expert by any means, maybe straight 30 would just be bad all the time. My dads/now daughters subaru runs 0w-20. Would changing to that keep more flow to the lifters?