You dont really need fillers with smokeless. With some smokeless..you do find the issue of 'position sensitivity' ,,where it can fall away/forward.. from the primer in such a way that velocities and pressures are not constant.
Don't wanna get over my head here,,but I think I've seen the guys talk about using a bit of bathroom tissue to hold the load rearward and more constant to the primer.
I use 5477 (when I'm not shooting bp),,,,it's bulky and I've yet to find a position sensitive issue with it.
Deadwood