Are you talking about looks only, or looks and effect? I'm not worried if ring #2 shows, only if the effects of both rings are applied.
Both effects will be applied, however as Echonite has stated, you will have to set up a set of rings that will only fit in the desired unused slot.
I have already done a similar effect but used it to create satchels/bags which increase carryweight. I used the unused slots 44 and 45, but had to set up a pouch/bag for each slot.
You might find that the CK throws up an error when you load your mod, complaining about " [xx item] used invalid biped object slot [xx] for [what ever race you chose to use]
The good news is that the error doesn't appear when loading the game or affect it, or at least i haven't come across any so far