Glad to have helped.

As long as the bag doesn't get between the foam and the sheeting, you're good.

If you use a rather thin bag, say 1.5 mils or so, the ability of the bag to fold into the contours can be an advantage. For instance, at the trailing edge, if you have 1/4 overhang, the plastic can find its way between the upper and lower sheeting (but not between the sheeting and the foam). If not, there is a void, the vacuum can crach the sheeting.