Does anyone have insight about lounge access on blended class itineraries? I will be flying the following itinerary and am curious as to whether I will have access to the lounges in Seattle and Taipei prior to the premium economy legs:

Outbound:
SEA - TPE, Premium Economy, Booking Class U
TPE - BKK, Business, Booking Class D

Return
BKK - TPE, Business, Booking Class D
TPE - SEA, Premium Economy, Booking Class U