I have two unused chimney thimble holes in the kitchen, both with a 6 1/4" diameter. I tried the 6" Insul-Plug and it did not expand enough to fit, the next size up is too large.
The chimney is currently only used as the water heater vent.
How can I permanently seal these? We are remodeling our kitchen and are framing/hanging drywall right up to one of the holes.