My 11 year old needs one for sports at school. We tried various ones in her primary school - they always hurt to start with - understandably - but continued to hurt. We even had her measured by Opro - at extortionate cost - and that still hurt her, to the point of bleeding gums. Are we doing something wrong? Any suggestions as to what we should do? Maybe I have to accept that dd has a strangely shaped mouth?? Thanks.