Contributed to numerous threads on this topic before;
http://www.iceinspace.com.au/forum/s...ad.php?t=41935
http://www.iceinspace.com.au/forum/s...ad.php?t=31029
http://www.iceinspace.com.au/forum/s...ad.php?t=28505
If these don't answer a specific question, I'm sure someone can jump in and provide the needed guidance.