daniel peterman wrote:
Here's a thought..
Cut the actual shape of the front and back parts of the channel from
sheet brass. cut the third side as a strip, shape to fit the contour and
solder/braze the three together. Clean up edges with a file. Could be
cut with a scroll saw accurately.

Would go along with that. Silver solder, "Eziflo", and the proper
flux would work. Everything needs to fit accurately before
soldering as this stuff does not fill gaps. A few locating pins
would help. Preheat the whole assembly with a nuetral flame until
the flux melts and then flow the solder into the joins. Do it
properly and only a small amount of solder is needed.