Smsnyder,
The Ear drum has no effect on a cochlear implant, as the electrode wire is placed directly into the cochlea, the concern there is that if from illness or other damage the portion of the cochlea had ocified(?) scar tissue filling the tube.
My son has had Cochlear Inplant(s) for 13 years now, when I have had him shooting at the club they have made him use ear plugs, they are required for everyone "so lets just go with that" was the line foremans call.
Other then football and other full contact sports, the CI inplant groups and audioligists we have worked with have had no problem with me getting my son into shooting sports.
Cochlear Corperation of America is our CI supplier.
Advanced bionics is another maker