I plan to install tile in my kitchen. After I removed the vinyl, I found out there was a thick layer of adhesive used for the vinyl on the plywood. I tried to remove it with floor scraper and adhesive remover. But the adhesive sticks to the plywood so hard that I can only get rid of a few. My question is can I just lay down the Hardibacker board on the old adhesive with thinset or should I remove the entire old adhesive before I put the Hardibacker on? I am going to screw the Hardibacker board as well.