906 or 915 ?

I’ve never actually measured how much height I’ve taken off.
I start with what I feel is a somewhat conservative attempt, but something I feel is possibly “enough”.
The first attempt rarely gets me the result I’m looking for, so I start tweaking the shape.
Sometimes I don’t quite get everything I’m after, and end up stopping......... not wanting to find water looking for a few more cfm.
For me, i do the SSR by feel.