I don't know if I'll put this in the right terms, but I think the reason some sighthounds need particular collars is that they have smaller heads in relation to the girth of their necks. Take greyhounds, for instance. If you use one of those collars with a closure the hound will be able to slip out of it. At leisure it should be adjusted so that it sits lower on the neck, but that circumference will easily slip over the head. Martingales are like instantaneously adjustable in the sense that on a loose leash they are comfortably loose on the neck but on a taught leash they get smaller. In the case of basenjis I think you can go either way (sighthound collar or not). Mine wear Northwind martingales.