How to set up a Surround Reverb?

I am trying to create a surround reverb in Cubase 12. The reverb I am using is East West Spaces II. This reverb has pairs of IRs which are taken from the front and rear of concert halls. The manual shows how to set up for surround reverb in Logic, but not in Cubase (Priorities EW!!!)
Basically it’s about setting up two FX channels and then routing the sound from your instrument track to both of these FX channels then out to your Surround Output.

The issue I am having is that only one send seems selectable - weird? In the capture below I find I can select Spaces 1 as a send for only one FX channel. Then again, I might have things completely wrong!