In your example it seems the bounding box is quite small compared to the whole arrow head drawing. Is that doing the trick?
Yes, I did it on purpose. There may be other ways, but I liked this one.
When I try to change the bounding box size, it is just shrinking the whole thing.
I used such sequence:
1. make a small group, for example from a short line
2. Open it for editing, add an arrow image
3. Delete the primary shape
4. Close the group and do not update the bounding box
In this case, the group remains small, and the arrow goes beyond the group.