I don't think we can define the generally safe usable capacity of a hand grinder by how much of one coffee can theoretically be crammed in up to the brim without making it inoperable. I also don't think I am the only person in the world who regularly grinds enough for two decent mugs with my hand grinders, but I guess we are just going in circles here. My target is quite reasonable based on a large collection of third wave cafe/roaster mugs from North America and the UK. I know I will have no trouble doing it with the Feldgrind because its hopper has enough room to spare while maintaining the same weight and overall volume as the Helor. The Helor misses the mark and imposes an arbitrary limit here for no good reason, and I don't believe the "issue" is unique to me. I've said my part, so I'm not going to keep pushing the point in this thread, but hopefully everyone is aware of any potential issues they might have with the capacity now.

On that note, let's give it a rest on the back and forth about capacity issues. They've been batted back and forth enough.

This looks like the best hand grinder made yet for travel. Will it fit inside an aeropress?

It will fit inside the main body of the Aeropress, but not the plunger.