I have the same issue , CNC Stealths .For the past few years I have ported the valley pan openings and gaskets to suit . On the new 505 I am still getting a little oil pulling through into intake on 1 cylinder , didn't have this on the 440 , 2nd time around.
I have bought Andys batwings and a selection of Superformance gaskets plus the Trickflow valley plate . I will be fitting these in the next couple of months , earlier maybe .
I think the ports on the batwings may need to be opened a little .
I know against the Felpro intake gaskets the Source port is bigger.

Tex

PS : I tried cutting the pan like you suggest , no luck keeping it sealed