I finally tried forge welding without flux after watching a guy in Reno do it

Last month I drove out to a hammer-in in Reno and watched an older smith weld up a billet without touching a single grain of borax. I always figured flux was non-negotiable, my old boss drilled that into me back in 2011 and I never questioned it. He kept his steel at a bright yellow, maybe 2300 degrees, and just brushed the scale off fast before every pass. I tried it on a small 8 layer billet this week and got a clean weld on the second heat, no inclusions I can see after grinding. Still not sold on doing it with anything bigger than a few pounds though. Anyone here run fluxless on a full 15 pound damascus stack, or does it start falling apart at that size?