I was just looking at the install instrutions for the Helwig rear bar. It's mounted in single shear. The pro's of the Helwig design is it is narrower so it will allow more clearance for the B-Body width set up.
The negatives are IMO... single shear mount is not as strong as Hotchkis mounting design. The Helwig bar is bigger than Hotchkis....not sure that's a great idea? Might be too much rate for a rear bar? HP2 would have a better idea?
Hotchkis mounting design ( rear bar) requires welding. Not a big deal to me but maybe for others?