I have a 2-macerating-toilet setup like you describe, but wouldn't try to do a gravity dump through a 3/4 inch hose. While the toilets "liquefy" everything quite well (no poop pyramid, for sure), as that stuff sits in the black tank, the solids still settle, so that the first part of your drainage is going to be a pretty thick soup. I use the good old stinky slinky, and it dumps quickly and thoroughly. Then I do the gray tank dump, then run my tank flushing system (if I'm packing up to leave), with a clear adapter so I can see the progress. It certainly drains, and cleans, more quickly and thoroughly than my previous non-macerating units.
