My $0.02 worth... I absolutely would *not* mount any kind of rotary powder thrower directly to the scale. I'd either find or make a thrower stand that sits/mounts off to the side. Throw the charge into the cup, and gently sit the cup on the scale. Or if you must, position the thrower directly over the scale, with a cantilevered arm - but I still *would not* mount it to the scale or the draft shield in any way.
Most powder throwers - in my experience - tend to get 'hung up' or have to 'crunch through' even medium stick powders (Varget/4895/N140/N150/H4350). The only reason the original AutoTrickler got away with using the Lee PPM mounted directly on top of the scale housing was because of the Teflon wipers that particular design employs; it literally *can't* 'cut' kernels like basically any other thrower on the market.