Tangerine Fruit Filling Out

The Citura tangerine tree fruit is plumping up quite nicely.  Whereas the began about the size of half and pencil eraser, they are now the size of a good-sized marble (not a big marble mind you).  In addition, the tree has had a vegetative growth flush since flowering.  I want to air-layer the tree when I get a chance.  That way I will have a backup in case something should happen to the original tree.