We have a whole house fan and I am looking for ideas on how to hold up a piece of rigid insulation placed over the grid opening. We use a piece of rigid insulation with fabric glued to one side to make it look a little nicer. We used spring tension curtain rods, but this tears up the paint where they seat. I was looking for something that would let me put it up, hold it in place and have the hardware be permanently attached to the walls, so I can rotate the hardware, remove the rigid insulation and use the fan, when fall comes put it back in place and turn the hardware to hold it up. I though about upside down shelf pins, but not sure how they would hold up over time in a hole in a plaster wall.

Appreciate any suggestions. Brian