I am pulling up a glue down vinyl tile floor in my bathroom and replacing it with 12x24 glue down cork tiles (3/16"). There is what appears to be 1/4" luan under the vinyl tile, although it's taking a beating as I scrape up the vinyl tiles. I am hoping to patch this up and glue the cork on it. However, whoever put the luan down left a lot of gaps in between sheets and in some places along the wall and tub. What should I use to fill the gaps, nail holes, and even out the places where I've torn it up while scraping up vinyl? Or, should I just put another layer on top and do what I need to do in order to make the extra 1/4" a non-issue? Thanks for any suggestions.