If you have the typical 1/4" patchbay, it will be a metal frame housing a bunch of little circuit boards with the jacks on them. Those are the cards I'm talking about.
The way I would do it is take 8 inputs (1-8) and then mult those to 8 more inputs (9-16). If you want to mult one input you'll use up two slots on your patchbay. Mult four inputs and use up eight inputs.
If you mult the way you describe, you'll end up multing the same signal over and over. If you want to mult a signal, just double it basically, then you need to think of the patchbay slots (cards) in pairs. So the lower rear of card one goes to the upper rear of card two. That is one mult. Then the lower rear of card three goes to the upper rear of card four. That's you second mult.
Hope this makes sense. Easy to show in person, difficult to describe in words.