I am very curious if you have ever tried different species of rootstocks other than M. jaboticaba? I was just thinking that if perhaps a much more vigorous Myrtaceae species( e.g. Eugenia, Psidium etc.) could be found that is graft compatible with the Myrciaria/Plinia group, it could push scions grafted onto it to grow and fruit faster.

 

Many years ago when I lived on the Big Island I did a lot of Artocarpus grafting (all jackfruits, since there were not any cultivars available for marang, pedelai etc. at that time). I would raise seedlings in a 1 gal. pot to about 12 in. A key thing I found was to have the rootstock actively pushing, so I would hit them  with fertilizer about three days before I collected scions. Using a side graft cut with an exacto knife handle that held the injectible-type one-sided razor blades, I would make the initial slice on several rootstocks at once and then go back  and make another paper thin slice on the inner side of the cut. This would lift out the latex that had bled out of the surrounding tissue. I would quickly insert the scion, secure with green stretchy tape (forget its name) and finish by wrapping the scion and graft area with parafilm.

This was done in a hoop house open at both end so there was good airflow and higher than ambient humidity with bright light but not direct sun. I also did the same under 20% shade cloth. Another important detail I learned was to only water the soil in the pot NOT overhead watering as any water getting into the graft before it calluses kills the scion. Depending on time of year (short day vs. long day) the scions would push in anywhere from 3 days to a week. As soon as they began to push I would vent the parafilm with tiny cuts to prevent water buildup under the film; a day or two later, they would harden sufficiently that I could remove the parafim. A week after that the graft would have callused enough that they could go out in full sun at which time I would also uppot them to 3 or 5gal, and fertilize again. They would take off at this point,filling out the pot and shooting up to 4-6ft over the next 6 months. With this method I would regularly got 85-100% takes. We produced IIFC about a 10-12 cultivars.