Right now, the spectate mode renders no cursor at the center.
The cross seems to be strictly bounded by a 36x36 rectangle at 1920x1080. I'm not sure about its blend mode though. Seems like a
negative or negative-overlay at 50%..?

why having to render the cross, if the inventory will not be rendered? that will look odd

It helps the viewer focus better (I'm biased here, but I make building tutorials and the cross really helps). I doubt that a few pixels in the center will make it odd. Anyway, I was hoping moving towards screen record-ish with replay mod. But, that would require to solve the walking animation (right now it's like sliding in ice), inventory, hp, hunger..etc.. I will continue putting it manually.