Hi Stephen,
The steel used in guards is usually quite amenable to reshaping cold. No need for heat or welding.
I spend hours making wooden blocks to suit the inside and outside profile of the guard. MDF works fine, and a jigsaw or a bandsaw is useful. Make a "stack" of these patterns, then relieve the inner patterns in the place where you want to indent the guard. Also cut off the outside part of the pattern in this region. Clamp the whole thing around your guard so that the guard is fully supported in the places on either side of the place where the indent is required. I usually end up with the MDF clamped in the vice. Now get a piece of wood to fit in the gap, with slightly rounded edges, and give it a whack with a big hammer.
I've done it lots of times with good results.
Good luck.
Leon
