Are they hard to make. What should they be made of. Will bumps destroy them?

 

I would make them from either chormoly or aluminum and use rod ends on each end. They shouldn't be hard to make if you can get the right size rod ends, check with local bearing supply places for them.
You won't want to ride on anything very rough with them. It might not destroy them, but eventually it could damage your frame. You will know when to rough is too rough....trust me.