My Williams F7 shell will not hold screws?

First, did you check the plastic sprues that hold the screws? check to see if they are cracked. IF so, a brass diameter tube will need to be glued in place to hold the sprue together.

Like PRR said....check the mounting post inside the body for cracks. A brass tube can work but if cracked I'd apply a solvent glue to 'weld' the cracked post and after a day of so I'd apply some 5 minute epoxy around the post and between the post and body side. And while you have the epoxy mixed apply a small drop inside the post.....not enough to fill the whole but just on one side internally.  This will give the screw something to grip if the whole is stripped. Allow the epoxy to dry a day or two and you should be good.

If the mounting posts are intact I drill them out for whatever size of plastic tubing will fit comfortably and won't leave the post walls too thin.  Trial fit the tube and cut it to length, then glue it in place with ca.  When the glue has cured, if necessary enlarge the hole in the tubing to properly fit the screws and re-install the body shell.

Pete

JB-Weld is my weapon of choice for this task.  I just fill the holes with JB-Weld, let it harden thoroughly, and then redrill the holes.  For split posts, I slide a piece of brass tubing on the outside that's a snug fit, then fill it with JB-Weld and then drill the holes.

Thanks everyone for the response.I will double check to see if the post that the screws are going into are indeed cracked.I just hate to keep taking the shell off and on because its plastic.