Heavy Duty Canvas?

[saltwedding]

I am trying to create a perfectly tight 100" x 58" canvas. I am using TWO sets of 50" wide by 58" tall heavy duty frames end to end, creating the desired 100" by 58" canvas area. My main concern is preventing warping with such a large format. I have stretched 64" by 36" paintings with success - but this feels like a whole new world. I would like to know what the best method will be to connect the two frames together (screws?) and what the most effective crossbar supports would be, as I have yet to purchase those. Help, I feel in way over my head here.