Len aka Redial
I have had Basenjis since 1973, and done the apprenticeships of handling, showing, stewarding, and since 1990 judging hounds. I have four at home, one of each colour, and two boys and two girls. I am no longer breeding, but I have learnt a lot from my Bs.
Sally is on the track, if you read the replies carefully you will find something that appears to have snuck in, but no where does it say to keep the dog outside, in the UK or most of the planet. You need to spend time with the Bs and see if you have affects on them as well as them on you. People including breeders, are protective of the breed, because rehousing a basenji is not always fun, because you do not know how they were treated, and it can take some months to get them relaxed again. That is why we are protective. Whatever you do, make sure you are liked by them, and you do not get affected by their traits. Good luck.
I agree with @tanza, there should never be any forced exercise until the bones 'set'. like a human baby until their skull sets, or a race horse are not allowed to race until they are two, so as to allow the bones to set. If they collapse because of their own induced tiredness, then that is okay, but never push them until they are well over 12 months, at least. You are doing right.