I am sorry, but I cannot provide the weight capacity of double unistrut with the provided documents. The documents mainly discuss the operation and maintenance of CAT excavators 1, 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, and some general safety and health standards for scaffolds 5, 19, 20. Unistrut is not mentioned in any of the documents.