Everyone goes nuts for the 'stack of dimes' look.. but in all honesty a good weld is a good weld and poor penetration is poor penetration no matter how pretty it looks.
Touching any airframe component on a certified airframe needs an A&P ticket. Experimental aircraft not so much.
FAA recommends post weld tempering for all TiG welds. I'd want to see that in a log book if TiG was used on an airframe I owned.
