With active 80-column display there's no way to activate hires page2. Instead of directly fiddling with 80COLSTORE it seems the cleanest way to disable the 80-column display via the official firmware entry point.
The ProDOS 8 Technical Reference Manual states in chapter 5.3.1.3 - 80-Column Text Card:
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80-column text cards -- and other Apple IIe features -- can be turned off
using the following sequence of instructions:
LDA #$15 ;Character that turns off video firmware
JSR $C300 ;Print it to the video firmware
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