I remembered on thing while I was out and about today. There is a training method that I HIGHLY suggest you start using (for both dogs), it's called NILIF (nothing in life is free). It is an extremely beneficial training method, that I started with my boxer and when Tiggy came along, he just feel into the groove, so to speak. I say this because I can't count how many horror stories about bad basenji behavior that I have read. With implementing this behavior with my boxer it was easy to work with Tiggy.
Boxers and basenji's both are extremely stubborn and take the meaning of bullheaded to a whole new level. Even though they are both completely different breeds, the things that most think are solely a basenji trait, my boxer has done the same. THe reason I say this is because I do know where you are coming from in the aspect of one 20lbs dog and one 67lbs dog, and both have almost the same mannerisms and personalities are very similar.
Okay, got on a rambling moment there. Now to explain the NILIF. It's just that simple, NOTHING IN LIFE IS FREE, simple explanation, they want a treat, they must sit or lay down. Same goes for feeding, go out the door to the yard, getting ready for walks, getting in the car, basically EVERYTHING they must work for.
PLEASE read this thread that I posted about it (I'm going to ask Admin to make it a sticky) it will explain it completely and has great links to explain it also
http://www.basenjiforums.com/showthread.php?t=2055