I've never done them as semi ripe cuttings....i would imagine either air or ground layering was the way forward with this as per most ericaceous species. Whatever you do, i would think that rooting would be slow and eratic.

Agree with Andy, one of our Pieris ground layered itself when a lot of dying leaves covered a stem without our noticing.

That is how I rooted mine,by layering,Mickey..takes a while ,but worth the wait..