I've worked with props and prop venting for many years and in a lot of cases "some venting" will help a hole shot......HOWEVER:
in messing with my current set-up on my current boat I have come across something weird...(to me)!

Set-up is:
20' Bullet, pretty heavy loaded,
Merc 260,
15" set back,
Prop to pad 1.5 over,
ProMax prop with 4- factory PVS and 4- 1/2" holes machined just behind the original PVS.

What I've noticed in messin'wit this thing is when I close ALL the relief holes the boat launches straight forward, (without even breaking over), and on top running in 1-2 seconds....even with part throttle launches!
When I start opening holes I start getting more and more of a break over, (and way slower on plane times), with the bow raising extremely high, then the mota revving as per the amount of venting increases.

I guess what's happening is the venting is really hurting on plane times when your set up is above pad as you are losing your forward momentum as the prop vents and loses contact with water that's prolly already aerated from the boat hull....What Say Y'all?

Here is a short vid with only 2 of the 1/2" holes open:

https://www.youtube.com/watch?v=_y_OkJICU_Q