Another frustrating dog problem

Now I have a weird dog question  

This is from a 3 yr old dog, no history of illness. He has been out on the show circuit this year and it is hot (85+F consistently for the past 2+ months), though he lives in an air-conditioned kennel or in the house. 

This was a routine semen check prior to offering him at stud. Motility & concentration were good. However, >95% of his heads had this ‘balloon’ shape that tapers sharply to the midpiece. He had a potpourri of other abnormalities, TCT, swollen/irregular midpieces, but nothing out of the ordinary. I have seen these heads occasionally in other dogs and considered them abnormal, but never in the percentages that this dog has them.

Could this be normal for him? I gave the owner options of rechecking in 2-3 months (accounting for sperm cycle & weather) or finding a bitch to do a test breeding. 
Has anyone seen these type of heads so prevalent in dogs that were fertile?