duly noted. The factory likely did flash-spot the "tab" on the original Deluxe with battery-tank frame, and that frame was likely a middleweight of the exact approximate time period. To me, this is not merely a restomod but a class enhanced build. Entirely a possible and logical period model.
The tab could easily be ground to fit any similar frame, and then brazed on, and this would have no negative effect on the structural integrity of the frame.
silver alloy braze flows at a lower temp than bronze so it doesn't change the frame, and removing said "tab" by touching it to the torch flame tip would make it fall off easily.