Layman’s rule? CFM X’s 2 = potential power.
258 rounded up .1 cfm.
258 X’s 2 = 516 HP. There est. is 540, 24 hp more, that’s doable.
Conservative? I guess that depends on how far you want to push it. The cfm X’s 2 is good for guys in the street looking for a good & respectable outcome or a casual but quick bracket racers.
What do you suppose? Thoughts?