Hi, is there a limit to the number of billboards that can be visible in one camera when using the mixed cam 8+8 compound. We are trying to put two overlay compounds in the flow so that we can leverage six different footages on the chroma tab to be made visible as six different billboards in a single camera. 
You can only do 3 billboards simultaneously. This might have changed with the new billboard rendering method in the latest version of Aximmetry, but the billboard rendering passes take up quite a lot of GPU, so any more wouldn’t be practical, at least for realtime rendering. I’m sure you can modify the Aximmetry camera blueprint and the compound in Aximmetry to support more billboards, but I wouldn’t recommend it for anything that needs to render live.