Hi jkd.. Probably what you are looking for is a young shimpaku tree, not a whip. Normally, when a phoenix graft is done. They use one young tree. This allows you to have multiple branches to work with. Also, you only have one root ball to plant. If you use whips, you are going to have to transplant a bunch of root balls. Also, seeing as how you have an excellent piece of driftwood. You probably should cut it down and carve it into a smaller and more pleasing and flowing design.
There is one instance where I have heard of using small whips for a Tanuki. This was done by Kimura. He actually grew the whips with triangular root balls. Then he carved the channels in the back and planted the whips into various areas of the wood. In time, he said that the whips root balls or triangles, would grow down the channel and into the soil. This is a very involved process. I would just go with maybe one young tree with many branches and use that.
Rob