Welcome to the forum. It's good to read the posts from breeders that appear here, because all your suggestions and information is welcome to all of us non-breeders.
Aggression is an all encompassing term. As pointed out above, there is quite a range! It is not unusual for Basenjis to be dog aggressive. Mine is, and I just avoid other dogs because I know his intentions are not good. Some are same sex aggressive and fine with members of the opposite sex, and some may just be making a statement when they are leashed. If you describe what you are seeing more specifically I am sure lots of people will have common experiences and possible training fixes to share.
I would love to see some pictures of Tucker, and welcome to the forum!
Welcome and kudos to you for helping with rescues! It sounds like Kowboy was a great introuction to the breed. I'm sorry for your loss of him and Indy. this is a great place to share and keep memories alive. I'll keep my fingers crossed for a speedy relocation back to your family in CA!
