The arms are open to different media. Here are a selection of pics of the types of materials I use on my dummy.
First pic is of some arms I picked up recently with glossy wooden arms. These are lovely to work with and are now my first choice. They make a lovely clacking noise, very crisp. And the wood is slightly lighter than my other beechwood arms, which creates a different feel. The offset nature of the back end of the arm is more pronounced, too.
I even used my new nunchuks in there to be a de facto arm. The stubby nature is what can be expected but the rubbery nature of the 'arm' is interesting. Gum & Bong sau is possible in this low down position, at least.
These 'give' a little when pressed and offer a different feeling.
(Some people think this is heresy, as you are fooling with tradition. I say Bruce Lee led the way - and that happened any way when the Pole was added to the Wing Chun inventory).
< 'A' for effort. The wheelbarrow inner-tube was a good try but you cannot expect to use this for heavy punches. The air just gives way to the force and moves elsewhere. If you were to pump this up to take the force then the tube would be bloated to exploding point, I bet ?!
This picture shows a yoga mat plus inner tube. It is different. Now the softer inner tube adds something to the mat alone. The tube also stops the mat unravelling, as I have not cut squares into it like the YouTube suggestion below.
I suspect sharper readers of this blog will see an uncanny resemblance to the Emperor Dalek below from Dr.Who. ;>