I dunno where I got .318, Tommy was looking at them and I guess I thought I heard him say .318 wall.
This calculator says 1 5/8 inch tube has MOI of 0.176 and the 1 3/4 tube has a MOI of 0.205, so the 1 3/4 is ~15% stronger than the 1 5/8 tube. I have no idea about the units used, just what number the website tells me. Now that I have my **** straight, is a 15% strength difference that big of a deal on a full size slowmobile? I'm thinking the S&W cage would be easier to do even though you can get 10 sticks of HREW for the price it would be for the cage plus shipping. All you have to do is notch and weld the cage kit and maybe bend new down bars in the back.