After playing around with this, and consulting the Vocoder instructions, this can be even simpler:

Set the Vocoder to 4 band mode - Now you only need to merge the 1st 4 CV outputs, using 1 Spider CV unit (instead of all 16 using 5 of them!)

Plus you can use that same Spider to invert the signal, meaning you only need to use 2 Spiders in total to make this work, instead of 7.

It really works!