I glanced at my copy of D14.3 2010  Specification for welding earthmoving construction, and agricultural equipment.

I noted that the prequalified joints within the standard has a variety of minimum thicknesses dependent on the joint type.

I did not note the 1/8" minimum thickness that resides in the "scope" of D1.1  (1.2 Limitations)

But it was just a glance.