Stallion length

Question
This may be a silly question but I have had a vet and a customer comment on the length of my stallion penis when aroused and one woman said he would probably not get mares in foal as he could not reach her cervix. I have one mare in foal and 3 others now ready to breed but one customers mare that is not in foal after 2 cycles. How deep is the mares vagina to the cervix and how long does a stallions penis need to be. He gets way in there and flags and I have had his semen tested and all is well. I have not measured him but the vet said he has seen smaller but that my stud was kind of short. Any help would be greatly appreciated.

Answer
Dear Susan,
          It is not a silly question at all! I have had 3 stallions with that particular problem (being to small) I find that the best way to ensure a pregnancy from a smaller stallion is to use Artifical Insemination, if you do not want to go that route then the only thing to do is keep breeding until the mare becomes pregnant. I'm not exactly sure how long the cervix is or how long the penis should be but the best estimate i have is about 15 + inches for a stallion.
michelyn