Need Some Help With A Leak

I had a custom box built for my f150 (Under rear seat) and I noticed it had lost some sound and sounded like it was fluttering when I turned up the bass. I thought it was the speaker but when I put my head back there it was comming from the box. I took it back to the shop, they said it was coming from the speaker wire hole, 5 minutes later they said I was good to go. The next day turned it up and of course, the same thing. Tonight I decided to just seal it up myself. I took the sub out of the box and filled all the corners with silicon. Put the sub back in and It took care of that problem. It makes me mad I paid 700 for the box and 6 months later it leaked. The issue now is it sounds like air is coming from the speaker ring or the screws. One screw even stripped out and wont tork. When you change subs or remove them, how should you put them back in?? Should you do what I did and put the srews back in the same holes or drill new?? If the sub is leaking from the ring what can I do? If the screw stripped can I drill new holes to secure the sub and if so do I fill the old holes? I plan to change the sub here in the next week thats why Im wondering, any help to make my box air tight up by the ring and screws PLEASE LET ME KNOW. I plan to change the sub 2 more times in the next week til I find the best sound.ANY HELP IS APPRICIATED!!!

 

What about when I chose the best sub and will not be removing it can I put something around the sub to seal all the way around??