Jonathan,
how come you never met up with Pedro Morales, and he has a school for Tropical bonsai.
http://www.pedrojmorales.com/There were also quite a few members on IBC from Puerto Rico, and one was a lawyer who studies in Tiawan, with the big names.
That celtis is supposed to be local to Puerto Rico.
Flambouyant, and Pride of Barbados are not easy as bonsai, the Delonix regia dies back on branches, and requires grafting.
Max I have seen is 6 branches and no real branchlets, plus I have never seen the root formation as it is in nature.
I could give you few local names but in zone 9b, you would be better off with the Chinese imports, Elm, Sageretia t, Fukien tea, Podocarpus, Serissa s, or local Celtis, Swamp Cypress, Ligustrum, Illex yaupon, Ebanopsis [ Texas Ebony ] or the Texas persimmon, and maybe Malpighia e.
Locally, great success with Tamarindus, Local Ficus p., Gmelina, Clerodendron [ from Barbados ] A type of ironwood, that is not the Brazilian type, Chlorphora t , and a few locals that still have to have their latin names added on.
What about custard apple and the other cousins ?
Good Day
Anthony