RAL INN said..
It's been too long since I've sourced the brass slide nuts but the thing to look for is that the step Corner is not sharp but has a slight fillet.
you only need about 30% more thread length in brass to get back to the strength of stainless. And those stepped slide nuts achieve this easily.
if anyone has a source for these, I'd like to know.
I broke 2 of the stepped ones. But they were old and a dubious history. They came off a Slingshot board. It's worth calling Kitepower, I know they are getting some spare nuts in soon. Also, Axis is supplying stainless nuts.