We are remodelling an older home that has 1×12 ceiling planks with gaps ranging from 1/2 inch to 1 inch. We would like to leave the planks exposed, but need to find some method of sealing the gaps. We’ve thought about Perma-Chink and other similar products, but weren’t sure if it would work on a horizontal surface. Also not sure what if anything to use for backing. Any suggestions? Thanks!