Hello. I am about to install my new bathtub. I have 4mil plastic over the studs and under the cement board. My question is that I'm not sure how to connect the plastic back to the tub. I'm not sure what the typical flange/lip of a tub looks like, but mine is a drop-in tub and its flange is small bump. It is not a nail in flange, just a hump at the ridge that returns downward. After the tub is in, the cement board will start 1/4" above the lip of the tub. So, do I just cut the plastic so a small bit overhangs the lip? What would I use to glue it? Would the final silicone cover up that material? Any help would be great - thanks.