Use a #20 304 stainless p-clamp(1 1/4) for the bottom
and a 1 1/4 u-bolt and strap for the midfork mount.Double nut the u-bolt strap so you don't crush the fork.

Quick,easy,strong.

Don't weld to the fork,you can have stuff brazed on.
Don't use a rivnut for the mid point mount,it will tear out of/distort the fork.Midfork mounts should use a tube through both walls of the fork,so that you don't distort/collapse it.

Braze something on or use something that clamps to the fork.