What would be the best metal for ceiling rafters?

We have framed up part of a metal building with square tubing for a living space now we are to the ceiling and cant figure out what would be better to use living space is ruffly 39 by 49 foot we want to be able to store stuff up above . We are considering either 3" 4.1 pound c channel or welded trusses out of... show more We have framed up part of a metal building with square tubing for a living space now we are to the ceiling and cant figure out what would be better to use living space is ruffly 39 by 49 foot we want to be able to store stuff up above . We are considering either 3" 4.1 pound c channel or welded trusses out of 1 1/4 square tubing like they did on the building rafters. I cant find any info on span or load of c channel but the trusses are good for spans of 40 feet but alot more work involved in building them. If anyone has any advice I would appreciate it we are going to go buy the metal this weekend
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