one more thing
One more thing I was looking at. As I don't have access to welding equipment but I really like the roller you have on it had an idea and wanted to see what you thought. What I was thinking was, instead of welding the pieces to the bottom of the barrel, make the X with castors attached at the edges and then drill 4 holes through the material holding the castors and drill holes through the bottom of the barrel and then bolt the castor X to the bottom of the barrel. Probably not as sturdy as welding but with washers/nuts on all sides so its not focusing the force on a small area of the bottom I think it would work. Any comments?