[Help] Questions about working with foam (attachments and cutting).

I'm making Nico Minoru's Staff of One. Non-colorized reference

Okay so what I'm planning on doing is connecting two dowels using this method since it has to fit into checked luggage. Then a foam ring and sphere for the head piece.

My questions:

• How do I attach the ring to the ball? I want to be able to swing the staff somewhat (just twirl it, not like take it into combat). I was thinking maybe a rod between the two to keep them straight and tape to keep them together. Is this viable?

• I'd like to cut a "trench" around the equator of the ball. One idea I had was to use this method and a chisel to "peal" the trench while turning the ball. Is there a better way?

• How do I attach the whole head to the staff?

• I want to go with staining the wood rather than spray paint. Any problems you can think of with this method?