My Addi kingsize didn't come with any foot braces and the standard wedge version of a clamp wasn't quite as secure as I wanted.

Two versions - long upper and a short upper version to cater for thick and thinner tables.
Print this with 6 lines / perimeters for added strength. Designed to take a threaded M6 rod (6mm) and secured below by M6 butterfly (or similar) nut.

Rather than bend the rod in a U shape as per the original Addi brace, I did a simpler 90º bend, and paired it with thingiverse 2226269, with a mod to put a 6.2mm hole through horizontally.