BioMax
+1y
1.75" x .188" tubing is pretty tough, but I don't think that I would use it on a full-size, I'd go 2" x .188" instead.
By the nature of the beast, in similliar sizes, square bar is stiffer than round bar by about 30%, but it is also heavier (not a minitruckers biggest concern). This doesn't mean that you should or shouldn't use either, just some FYI.