Hypo does seem to be one of those "recessive" mutations with co-dom tendency. I have a female het hypo with that bright clean look. Thing is if you really wanted to breed a het hypo male you could buy one pretty cheap now and know what it is 100%. But if you have the extra females and time by all means breed him and see what you get. My original het hypo male had that look and half his babies did including the now proven het hypo daughter.

A belly shot and a good head shot might also help to figure out if he is a known co-dominant like fire or vanilla.