Long story short, I was given quite a bit of lay loose vinyl floor planks and was planning on installing in an old lake cabin which currently has carpeting. My issue is the floor of the cabin isn't level and does have a little flex. With this in mind, do I need to reinforce the flooring before I install the vinyl planks or can I leave it as-is and just glue them down? If it's ok to glue them, is there a specific type of glue I should be using? Appreciate it.