I plan on classifying my material down to at least 1/4" so would expanded metal work as well as small riffles or should I use both? The area will also more than likely be heavy with black sands so I was thinking of running miners moss over some vortex to keep from loading up mat with black sand quickly. My understanding is that larger size material needs riffles where smaller classified material may not? I haven't done much sluicing in the past so please correct me if my thinking is not correct!