[maple_leaf_eh]

If you were repairing an old house and you had to move an interior wall, the most workmanlike approach would be to remove all of the last guy's work and start from a known-good surface. The men who will have to make the welds know their own limits, and how much effort is required to achieve the result. Take heed of their counsel

There is a risk that came to mind when you mentioned having two halves. Years ago there was an American firearms magazine called, Firepower. Their specialization was legal fully automatic weapons. In one issue the editor and his writers made a BAR receiver from three demilitarized sections. After welding it was set aside for tempering. With bang, one of the welds exploded. After very close physical examination and some metallurgical tests, they discovered they had WW1, WW2 and Korean War pieces. Three contracts, three factories, and three steels. As I recall, they broke the remaining welds, retempered the three pieces, redid the welds and retempered the receiver. Of course at the right percentage of assembled, it was reported to the authorities for registration.

The question therefore is, have you tested to see if the steel in both halves is the same? If yes, have at it! If no, you may need to use different rods or wires and different settings.