Quamen have been making flatland parts inhouse in California all these years. Their set-up is comparable with the one of S&M, FBM, or any smelly garage company that wants to make things at their own place using whatever equipment they have available to make it work. Welders, benders, cutters, CNC machine, jigs, and metal pipes everywhere. You get the idea.
Here are two flatland products they've got in their line right now; the Clad G7 frame and the Mobile Armz crank arms.
Check out these ultra light flatland crank arms from Quamen: Low calorie 22mm chocolate "flavored" 160mm flatland crank-arms; human-friendly design and taste.
Clad G7 Frame: Specs: 75ha, 18.8tt, 12.75cs, euro bb, 4.3lbs.
Info: Quamen signature flatland frame, Optional brakemounts, 3/8 pops included