There aren't any. When placed as a ghost, all versions of the Flare Stack are invisible until built. The ghost is there, it can be moused-over, selected and removed, but it's not visible. I've not looked at ghost graphics and what it might take to fiddle with them, but this becomes a bit problematic on Space Platforms where everything is placed as a ghost and may spend some time in that state.

edit
Please disregard. I was using one of the several other clones of this mod that had this issue. I've not started using THIS mod, and THIS mod does not have the issue. My apologies.