I have airlayered close to 1,000 lychee trees at this point. I have yet to get an atemoya airlayer to take (with about a dozen tries). The wood is very weak and I think the fiberous bark helps provide structure that holds things together. I do know that after layering the branch is highly susceptible to wind damage and will snap off at the slightest breeze. Maybe I need to use a different technique than I do for lychee. I hear that they do it in Australia on fresh green shoots by using a clip that slowly cuts off circultion as the plant continues to grow.