This is for everyone. Terrain Tips.
Firstly if anyone dies then put some default ground tiles in an empty level to walk around on to test it and you wont die. When the Terrain is then placed correctly you can delete the ground tiles if you like you wont need them.
A couple of things - firstly - I have said that its difficult to work with full level size Terrain as it makes it difficult to see anything else in the level.
Even placing it is difficult as the render shroud which lights it up to a ridiculous extent makes seeing and placing it difficult.- though if you zoom out - you should see its outline near to the world size extents all around. You may find playing with the render shround size may help you see more clearly.
Make sure it dont exceed the world size and when you place it that it does not extend anywhere on any side beyond the world boundaries so you must get it in the middle or it wont show up. If the model is too big try scaling it down in script which may help you get a feel for placing and working with it.
Though you dont need it place some default ground floor tiles in an empty level so you can stand on them and then place the Terrain - run level - if you cant see it then ask yourself where is it?
Either its not rendering cos its beyond the world size somewhere or its hiding above or below you - thats all the options. If its hiding place some floor tiles a few levels up and re run test level with terrain in there and look down to see if you can see it.
You may need to try placing it a few times to get it to show up as placement is difficult and as said FPSC wont render it if its outside the world boundaries anywhere at all.
Trial and error is how I learned to place it which why you should use an empty level to test it out before trying to place it in an existing level.
I got the Terrain in to a finished level perfectly placed as you can see in the Screen Shot. If I can do it, so can you.
I said its not easy but could not be said to be hard either - a little patience is required - thats all.
Hope that helps.