Okay, if you TP to Koss (62,204,254) you will find yourself in a room with a big window. This window has the inner side set to be an invisi-prim, ie you can see through it but for all intents and purposes it is opaque, as such objects outside are culled. I'm using these in my house quite effectively to clear my view of the horizon from horrible malls and such.
Anyway, if you look out of this window to the left and up a little bit you will see several prims hanging in the air, a square pillar and a 'gutter' at the top. What I'm trying to figure out is why these are not culled while the entire room they are contained within is. They do not intersect with the walls (which as you can see have been culled just fine), and yet they are still visible.
If anyone can figure out why this isn't being culled it would really help, as I'm at a loss of what to do in order to place it so that it is culled correctly.