Max groove weld thickness for GMAW on stainless steel.

My boss wants me to weld 1 1/2" thick stainless with a single GTAW pass and weld out with GMAW .045 solid wire & Tri-Mix backing. I have always been told as a rule of thumb that 3/8" was the max thickness for GMAW on stainless with sold wire. Is thiis correct?

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for multi passes, i dont think there is a real limit on thickness.
but you are right to be concerned because cold lap is a concern