It really was a difficult journey too. I eventually had to triple the amount of RAM in the iMac to deal with Terragen 2 either crashing, or not formatting the finished render. To anyone doing hi-rez rendering like this, take my advice and pack in the maximum amount of RAM your computer will allow (mine is 16 GB). RAM is amazingly cheap now and makes a huge difference in the computer's overall performance while under a heavy load.
Nicely done.