Gee I don't know. Why do you think most of the large pet forums have these rules? Most are on puppy selling sites (like this) that make THOUSANDS of dollars a day. They really don't want to risk losing that profit.
Boxers are like cookies you can't have just one :)
Update. Hi everyone. Well, at this point, my girl's Kimbertal lines are not an issue, this is her last litter. Otto was fixed - it will be 3 weeks on Tuesday. He is doing well, all recovered. He is getting along fine with Fergus (who is neutered) and all the other dogs. Isabelle did not get pregnant and will be spayed before the end of July. Hazel will be spayed after her last litter - due July 18. My vet and many others begged me to not neuter Murphy - to let Otto's hormones calm down and see how it goes. I have temporarily agreed. I wll admit it is a huge pain to keep them seperated, only one allowed out at a time instead of the doggy door (we have 4 fenced in acres for the dogs and a doggy door, they come and go as they please, normally). He and Otto still growl at each other when passing in the house. If they see each other outside, it is not so bad. I don't know how long I should give this before a decision is made on altering Murphy. I have a couple of requests for AI for him in the fall. But is gets mighty cold here and I do not want my boys out in the cold.(one has to be out whie one is in, except at night, Murphy comes upstairs with me. He won't stay up there during the day!) Any suggestions on this? I do not want my boys to fight, which was the reason for the decision in the first place. Otto and Murphy never fought until the end of this last heat. I welcome any advise. I do not want to have to rehome Otto or Murphy, we are too attached to them, they are my boys! I did find an excellent new home for my Aiden. He was 5 months old. I adored him, but he was at risk being another male in the pack. His new home is fabulous!
Thanks for any help getting my boys to get back to their old selves!