Sugar apple rootstock is better in the tropics and produces smaller trees. I am sure in the subtropics sugar apple rootstock would keep the trees smaller as well. Pond apple is a poor rootstock and has repeatedly failed in Queendand.. Atemoya rootstock is reputedly prone to disease in wetter areas but it may depend on variety. I am curious how reticulate and soursop would go and suspect the custard apple may be alright.I bet ilama would be alright in warm climates as atemoya rootstock.