If you get the chance, go to this this link (TBIT real-time arrivals) to see what flights are arriving at your time (past flights don't stay in the system for long, so you'll have to look at before 11am PT to see all arriving flights). That will give you an idea on how long Immigration/Customs will take.

IIRC, 11:15-noon isn't so busy at T4. Be sure to use the elite escalators on the West wing of T4 check-in (closest to TBIT), though if you get to the top and see that the regular line is shorter (no one on the long walkway overlooking ticketing), then get out and go around to the regular access line.