I have two that are about 10' tall. They are in full bloom and the scent is incredible. I have them planted at each end of my patio. I'd like to take cuttings but I read that it's difficult.
I have just gone through 10+ pages of info on this plant and thoughts on propagation.
It seems this one would benefit from bottom heat during the rooting stages. Which is so contrary to when I do to other medium wooded plants.
One reference indicated rooting in 30-100 days with bottom heating application to the soil.
Other than that, the other reference was by seed, that once stratified (did not indicate the method) that the seeds would germinate freely for up to six months afterwards. This is a 'true to seed' parent, so the quality will not falter and will likely behave much more aggressively and with more vigor than a rooted cutting.
I am sure you ran into these same thoughts. I would try the heating pad method ... if it works you solved the riddle!