I worked for years in the retail and contractor home center business. The company I worked for also manufactured wood roof and floor trusses. These trusses were supplied for regular homes, commercial buildings, municipal buildings, large apartment complexes etc. Each truss is designed for an intended load with specified bracing points to make the truss system work as one unit. If a truss is not designed for a specific load to be hanging from it, then you are taking a real chance at a failure of the entire roof . When a roof truss has a load on it, ex: snow, the webs in those trusses push down against the bottom cord and then back up to the top to balance or absorb the load. Hanging something not planned for on the bottom chord could cause failure of the entire system because if the plates on one truss becomes comprised, it can affect all the trusses.