Big chief bbc indy manifold

I have a brand new indy bbc big chief intake that is going under a psi d-screw. The rear of the top of the intake needs to be opened up to match the psi distribution plate. Should I open it up the 4 in width all the way back or should I cut it to match the key hole shape in the psi plate? I am leaning towards the keyhole shape but not sure.