Highest flowing sbm heads?

MMissile said

This is the sheet for my heads, from my builder....

View attachment 1716072693

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At this point I guess I only have one question. With the amount of money and time spent on doing a head like this why not a w8 or W9? That head totally stalled at .600 and actually backed up a hair. A W9 would have kept climbing to 400cfm.