300cfm from 452’s is a weeee bit more involved that following the MP templates.
I had someone send me some stage V‘s
that they had template ported using the stage V specific templates, then finished off the rest of the ports with some sanding roll work.
Flowed in the 240’s.
They sure “looked” like they would have followed more than that.
Don’t forget...... the instructions with the templates warn against touching the short turn........ so if you really follow the instructions to the letter....... you’re only going to get so much flow.