Bayou Classic 62 Qt. False Bottom size?

I got my hands on a 62 qt. kettle that I am interested in turing in to a mash tun. After measuring the inside diameter it looks to be about 15.5" ID. Doing some research it looks as if 15" is a standard for mashing in a keggle. Anyone have any experience mashing in the 62 qt? If so what size false bottom do you use? Any reason I could not use the 15" false bottom that is readily available? I currently have a domed 12" false bottom that I've used in an igloo cooler. Could I use this and save myself a few $$? Thanks in advance.

Here's what I did for a false bottom modification to fit in a stock pot. I'm sure you can use what you have on hand with a little creativity and modification.