I don't have a drop tube, I think I can guess but what is it? I tried like you said to swirl the powder, put it in a little bit at a time and tamping the case to get the powder to settle, but even then that only got me to 16.8gr. I tried putting the powder a little at a time and packing it in with a dowel just to see, no better results.
I wanted to load some 50 gr and 55 gr bullets so I am thinking of starting with some loads for the regular 218 Bee and working up from there.