Mgbruch: I use soft nails. I use a 3/8 steel plate drilled to 3/32 and countersunk to produce a 5/32 head. You can adjust those dimensions to fit your nails. I heat the nail up with a torch while the nail is clamped in a vise, drop the plate over it and form a rivet head in the countersink.. You can make the process easier by using a finishing nail and dropping it through the plate, the head will bind on the plate.
If you make a paper template of the shaped tang extension, cut to a 45 degree angle on the butt side, you can transfer that to the flat butt metal. That will roll up to a good fit. The angle of the cut is not critical. You need to file the flanges to get a close fit in the solder joint. It is easy to do the 45 before you bend and it will be close.