Aluminum tread plate for casting deck

[Bob Jordan]

I have a 1542 Tracker jon boat. I'm building a casting deck between the front step and middle seat. Level with the top of the seats. 52" wide that narrows to 39" at the front step. The frame is light steel bed frame material because it's free and the welding is free too. There will be 4 support bed frame rails front to back 52" long, 10" between them. It will be suspended between the two seats for easy removal but latched down for safety. My problem is figuring out what gauge aluminum tread I need. The lightest possible weight is a must. I need the very rock bottom required to hold me and my lawn chair without flexing. I'm a185lb. old fart. I've seen a few aluminum tread sheets online that are used for catwalks. They are very thin. It seems they would work fine since they are designed for catwalks. Your opinions are greatly appreciated. Thanks!