Plastic stocks are a pain to bed... they were designed to simply tighten all the screws and let the stock bend around the metal...
You will have to remove a lot of stock so the barreled action can lay in the stock and be bottomed out without the stock "being squeezed open by the metal"...... Then you can remove it and put a lot of bedding compound where you want it. Let it cure without any screws inducing stress. Make sure the barrel is considerably free floated and centered in the barrel channel. All the bedding is going to do is be a spacer between the ill fitting plastic stock and the metal... it wont adhere well to the plastic stock so small holes into the stock and mechanically locking the bedding in place is advised.