Hi, Well, I got a mango cutting to root this summer. The cutting was about 8 inches long and semi-hardwood to somewhat green. No thicker than maybe 1/4 inch. I think the heat we have helped to kick it in.

Would have to add that the roots are VERY fragile and breakable as they develop. In fact I broke a major root pulling out of the propagation box. I have since moved it from my propagation box into a small pot to root the rest of the way in there. That way it won't be disturbed. I left a few leaves on the cutting, but cut them back to reduce transpiration. I did use hormone as well.

The cutting was from a seedling plant and was just an experiment. I don't know if more mature wood would root as easily. If it did maybe people would be less prone to graft them?

But it sounds like you have a lot of plant material to work with. I'd certainly try to graft it onto a seedling rootstock.