mounting fixtures configured to mount said {HEAD ~ device} on a head of {TAIL ~ said first user}, 
mounting fixtures configured to mount said { HEAD ~ device } on a head of { TAIL ~ said first user } ,
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH