Hmmm 20 tph?
What's the service going to be like? If what you say is currently true, 12 N's and 8 W's? IIRC when the B terminated along with the N in Astoria in the mid 80s, there was more B service than N probably because of the ridership along West End vs. Sea Beach.
No matter what there will be congestion. Heck I'm at the courts right by the Astoria Blvd. station frequently and at the peak of rush hour there are times where a train is stalled at Astoria waiting for a train to head to Manhattan so it can make it's last stop. Turning 20 tph will probably back things up to at least 30 ave. I guess that's why they're doing the peak express. To cut local congestion.
=)