(Sorry in advance, this is my FAVORITE question, lol)
The wood is fine, as long as you don't fall down on it and hurt yourself. It FAILS whenever you master standing on the flat surface and want to be challenged further -- It has ONE adjustment -- SUPER EASY and that's it.
The balance balls and any spring loaded trainer are GREAT for strengthening ankle muscles, but HORRIBLE for teaching the proper technique of stunting. Imagine holding the foot of a flyer and their foot moving around in your hand while they are in your hands. You will NEVER be able to balance them. This is the opposite of "LOCKING OUT" because they are constantly moving their foot trying to BALANCE themselves.
You don't want the flyer to BALANCE, you simply want them to keep their weight over their center of gravity and LIFT UP (think of it like holding a broomstick in the air -- Easy because it is not moving around -- Now try that with a pool noodle -- Good luck).
This is where the Stunt Stand® comes in to play. 5 Patented Adjustable Inserts that allow for ENDLESS amounts of DIFFICULTY -- From the easiest, to the most difficult settings. You can practice squeezing your ankle muscles tight WITHOUT movement in your foot or ankle and practice pulling the body position while keeping your leg locked and chest up.
This ability to practice the right technique of squeezing the muscles and NOT moving them to balance is what allows us to GUARANTEE results.
Think of it like the world's best batting cage or driving range in golf. This is EXACTLY how you should do it in the air, not BALANCING like other products try to say are good for stunting.
Don't take my word for it -- ask any cheer coach that has held a flyer's foot moving around in their hand and they will agree -- trust me.