Welcome back.
1) Maybe consider the rear left corner instead? (position as if facing the front door)
The sensor will be of no use if hiding behind a curtain.
2) Are you considering a keypad upstairs to arm the system at night?
If not the sensor will need to be a walk-through zone anyway, could be front right adjacent the door but opposite the keypad.
However, if you arm it upstairs another option is make the hall full alarm and leave as post 5.