What I have seen and experienced of aluminium brazing, including when it is done by a qualified welder, suggests that it is stronger than glue but considerably weaker than, say, lead.
Failure in service of that coil mounting would be likely to permit vibration of the coil which would result in fatigue failure of the other coil mounting. The coil would most likely then rotate with the flywheel and become jammed between cowl and flywheel, stopping the engine and necessitating the replacement of both coil and cowl. However there is a possibility of the fan becoming involved, which would probably result in the coil being projected vigorously through the cowl. This would be quite dangerous to nearby personnel. I would therefore classify what you propose as too dangerous to be seriously considered. However, you are doing it, I'm not - and I wouldn't. It is your responsibility.
