Cliff to Canyon

Okay,

For my next map, as some are aware, I need to recreate the canyon effects found on Tattoine. Ive thought about the options, and it would appear to me that the best aproach is to simply remodel the cliff models. As such, I located all the cliff models for the 2 layer tall clliffs, and extended the hight for all of them (Manually, so as to only adjust the highet of the clif, not the slope of the base terrain).

The effect is exactly what I wanted, no major problems, except two.

1) For one reason or another, the flat (not diagonal) cliffs that face tward the top of the map do not work. The ones facing left right and down all work without any problems. Im positive I have exported all cliffs for the doubled highet and adjusted them acordingly. What could be wrong? Am I missing a cliff model from another folder?

2) Sence the camera is directly behind the character at all times, if you aproach the cliffs to closely then you see stragith through them. This would not be a problem if all you saw was a dark abyss, however, you don see thorugh the basic cliff structure as well....So although the cliffs appear to be taller then the camera, when you look behind them you see the normal low level terrain. Is there a way to change this hight to be much higher as well, so all you see is the black sky? (Without skinning a new alphaed terrain)

Thank you for those who take the time to read this rather long thread, Ide really apreciate some help.