Yep, it should. Just put the gumshields in a bowl of boiling water. Leave it for about a minute, take it out, shove it in your mouth, bite hard and press them against your teeth by sucking. Should mould into the shape of your teeth.
If you buy a moldable mouthgaurd, you should be fine!
Yes, just mold it! Plenty have instructions about boiling them in hot water and then molding. Smart man to use one too, really helps to prevent concussions
