Question: workbench configuration drop_offset

I am a little confused…
I have redone my worbenches and thought
"Would be nice to have them acessed by just one way". So i went through all the others like blacksmith forge and took the adjacency flags imported them into my workbenches. So far so good. After i recognized that playing around with that needs to re-position the model and redo the collision shape that the little ones can reach the center to pick the workbenches up.
After seeing through that i realized that crafting got odd.
Sometries the collision shape was to big to drop crafting materials, some tries later the crafter got stuck and crafted unlimited after finishing an item.
So i thought: Edit the drop offset for the table and the crafting material i/o should be at the border of the workbench and everything will be OK.
But i cant get it to work properly. The drop offset is, as i see it, limited to the adjacency box or its center is the center of all adjacency boxes possible.
And the crafting output is not defined by the drop offset.

So pls someone experienced out there bring light into my darkness and give me an link or description how to do it.