Originally Posted by Mizkaki

Great White,

Horizontal or Vertical bobbin axis has nothing to do with whether or not you can use a double needle. Both your 328 and 319 have front load bobbins not side load.

We need to only consider whether or not the hook can pick up the thread from the back side of both needles. In a side load such as this Kenmore that we are discussing. The hook is passing to the right of the needle (the scarf side).
If you put a second needle in to the right of the first one it will hit the hook and if it is placed to the left of the first needle the hook will not pick up the thread loop.

Clearer than mud?
Cathy