The sole can be tempered, shaped, hardened, and draw to exactly the correct temper before installation if you use epoxy. Even a 400-ish degree silver-bearing solder is going to risk drawing the temper of the shoe too much when applied, though this is probably a more traditional way of doing it. I read somewhere of brazing on the new sole and immediately quenching the whole frizzen, it seems that brazing temperature is a little higher than that needed to harden the frizzen fully. The temperature needed to draw back the cover and toe and to draw the sole (if required) is nowhere near the melt point of brass, so no danger of loosening the sole during those operations. It might have been Dave Person who wrote of doing this. Me, I'll just save the trouble and use a steel-filled, structural epoxy.