Thanks Roger,
yes, that design would allow you to sharpen right to the end. I've seen a similar thing combined with a rounded recess for locating the index finger.

BTW,'World Woods in Colour' by William A. Lincoln lists Pterocarpus angolensis first under the name muninga and also offers mninga (Tanzania), ambila (Mozambique) and kajathout (RSA) as well as kiaat and mukwa.