For tunnels I will only use the stainless rivets. They form a spike kinda end when compressed, not an open end where the ball used to be. Tougher than nails, easier to grind em and punch them out than try to drill them. Regular rivets will loosen off over time. I buy mine from Accufasteners in Edmonton, but I'm sure you can get them somewhere near you. Maybe call Accufasteners and get the right type before you start your search. They are available in 2 sizes and are $.43 for the short ones and $.47 for the longer ones. Ask them for the same type of rivets that Chad from CR Racing uses.
