Unfortunately, I am not going to be 100% sure until I finish the design and get the exact sq ft of my material needed, and multiply that by thickness and weight. However, I went with the T6 Aluminum because it is right at 1/3 the weight of mild steel which is currently used for knights armor. The knights armor was my initial source of info on this project, and they weigh in from 75-125 lbs depending of course on how much they throw on. My hopes are that with this little of material, and a thin 16 gauge or so sheeting, I shouldn't be much over 50 lbs at the most.
The only thing that I am still not sure of yet, is how I am going to build the fasteners in to attach everything, but that is just going to take some time in AutoCad looking everything over. If I can pull this off for less than they charge to build you a suit of arms ($2,000 or so) then I think I'll be ready to take on my project and get the fabricator to work!