Yea the notch is not a problem. If you do fill it your drive height will be way off also.

Peak hp was at 5500 599. 6000 hp was 592

Was it dynoed with your exhaust or dyno headers? Do you have dyno sheets?

This is a hydraulic motor

Drive is 2.50 below the hull pad

Also with dyno headers to your manifolds is a dramatic loss. Mild thunder will chime in again but I think mer recently did a test on similar power and it was around 40hp from dyno headers to manifolds.

Harden makes a tubed headers called cyclones that will work with my risers that are all stainless

Basically my manifolds are the same manifolds that came
On HP 500s or Gil type manifolds which I read somewhere rated for 500 hp I'm wondering if they're choking me out

Yes. I know the ones you have. GIL replicas. As far as manifolds go the best ones are the ones diamond sells. The old KE design. I'm in the same department. I have gils for my builds and now second guessing myself.

I dont think youll see a gain from the short tube cyclone/gil replacements.

I think the heads are probably your limiting factor from keeping it how a 27 fever should run with 600hp. Legit 600hp.

Okay which heads I run in salt water but flush all the time