I was just about to order way more Kailh hot swap sockets than I need because it really is the ideal testing pad. But I really didn't want to pay essentially ~$12 for a single one and wait for a week plus. 

I was just starting to breadboard the 4x4 practice matrix when it hit me. Breadboard guts! I tore the power rail off of a cruddy old breadboard and here we are.