Wow, lots of interest!
Below is a picture of the 3 disco's I have. The one on the left I made 8 years ago, it's perfectly seasoned and you can see the difference in color, it's 20". The middle one is actually bigger, it's 20.5" diameter. It's never been cooked on. The one on the right is the one I used this weekend - it's first cookout. It's actually 22" - I thought it was 24 and the others were 22 but I was mistaken. Knowing that, I personally wouldn't want a 24" on the river. The 22" weighs significantly more than the 20's, it looks a lot bigger in the pics, but when stacked only looks marginally bigger. (like 3/4" all the way around, duh.). 20" is perfect on the water in my opinion, but the thicker/heavier 22" does heat a little more evenly. I'll be looking for another larger disc for our car camping rig.
The problem is I only have two extra's (I can't give up mine, need it on an upcoming trip, plus I'm kind of attached). I just talked with Bob and he's in no hurry and said he could wait a few weeks. So Zach as much help as you are to all of us I'm inclined send the 22" to you for postage (unless you want bigger, then I'll have to source a disc). I drive by Jim's house every day (and have stopped in several times recently, but there's never a green boat there). I'm sure we can hook up one of these days.
Thanks Bob for deferring! I'll get looking for more discs.
Edit - I have no idea why that picture is upside down. you'll have to reverse the descriptions - left is right, right is left, down is up - holy crap it's almost anarchistic.