If it is possible to route inputs 1-16 of the 16R as network inputs to channels 17-32 of the SL16, as the manual seems to say, you can use 32 channels. But in stagebox mode "off" the 16R does not share flex mixes/auxes and main mix with the SL16. You get one main mix and 10 flex mixes on the SL16 and another/totally different main mix and 6 flex mixes on the 16R. To use the full potential of the SL16, a 32R probably is the better complement, because it serves all 32 input channels and 16 flex mixes on stage.

Thanks. I'm actually going to be right beside the stage, so all I really need is access to the additional 17-32. I am fine with the main/aux mixes as is. But you are likely correct. I think it is going to come down to what is available to rent at the time.

I can't wait to start playing with it!!

It might well be that the new stageboxes will deliver, what you want to acchieve. Unfortunately there is no manual available yet for the stageboxes, so this is just my personal guess. The new stageboxes do have some processing on board and they will be part of the full range AVB networking, so it looks like they basically function in the Stagebox Mode of the Series III rack mixers (including the routing in groups of 8 channels), plus some more features.

Just add a NSB 16.8 to your set-up and route its 16 input channels to channels 17-32 of your SL16 (the second fader bank). Adding two NSB 8.8 also results in 16 additional input channels, but also makes 16 output mixes available. Two of them would normally be used as Main Outs L/R, so there are 14 flex mixes available via XLR outputs.

I suppose we will see the manual within the next days, because the stageboxes will be available at the shops soon.