Fiberglass box face not sealing

This is my first fiberglassing project and I think I need a little advice.

I am building a box for my subwoofers out of 3/4" MDF. On the face of the box i have cut 3/4" mdf rings out to extend the subs out from the flat surface of the box (only 3/4 of an inch from the face, rings are glued onto the box). Material was layed and glued down with 3M Super 77 spray adhesive. Everything was pulled tight and i completely coated the fabric with resin. After 24 hours I applied the first coat of fibreglass. This fiberglass was purchased from Home Hardware and has the matte strands in it.

I thought this would be the easy way to go. When the fiberglass was dry I cut out each of the sub holes. When I cut out the holes the fiberglass started to life around the edges of each hole. The fiberglass is completely solid but it is lifting off. Is there any way I can just glue down the fiberglass around each hole. I am at the bodyfilling stage right now but do not want to bodyfill then have the entire surface crack because of one loose section.

If anyone can help they would be a life saver.

Thanks