Mark, you can transplant down into a 3 gallon Air Root Pruning Container (ARPC) provided that the tree's present root system is still small enough so that when spread out horizontally, the roots do not yet reach the sides of the ARPC container. You want the root tips to grow into the container's sides, so that they will be channeled into the air pruning slots. If your tree's roots are now too large for the 3-gallon container, you can purchase a couple 5 gallon ARPC, or let me know and I will sell you (at cost) a couple 5-gallon ARPC. NOTE: When planting into a ARPC, after the root tip grows into a pruning slots, and becomes air pruned, they will begin producing new lateral roots starting from the tip back 4 inches.. This is known as the "4 Inch Rule". Later, when the new laterals reach the pruning slots, they too will be air pruned, and they too will produce lateral roots. So where you had 1 root, you will now have 16 to 20 roots. Be sure not to let the tree remain in the first ARPC too long, and become root bound. You will want to transplant it into a larger ARPC for additional root pruning. After two or tree up transplants, your tree will have many many 1000s of roots to support lots of healthy growth on the above ground tree. - Millet (1,029-)