I have hinge cut a fair amount of ironwood over the past few years, hickory is the only species that I can think of that I have hinged more of. I have had good success with keeping the main tree alive after hinging from what I remember. (Caveat - I haven't been in my hinge cut areas now for many months, but I will be soon.)
As I recall, while I mainly try for a good hinge...I will also just cut some of them off and let them drop and then drag the "loose" trunk up and on then on top of another hinge or a nearby stump, etc, just to get a little more horizontal trash going. Kind of a little mini-teepee effect.
FWIW, I asked a qualified forester last spring his opinion of what ironwood was good for, his answer, "Dulling chainsaw blades.". I concur and normally leave few of them behind when I work through an area. While I do hit hickories hard too, I never eradicate them from an area. While not the best deer tree in the timber, hickories are far better than ironwoods IMO.
I have never treated the ironwood that I have cut, I'll keep an eye out this winter to see how many are still living, etc.