As a general rule, your scenes' file size shouldn't be more than half of the physical RAM which you have. So, if your scene is 100 MB after you save it, you should probably have at least 200MB (256, of course, there are no DIMMS set at 200MB!). SO, I would say that 512 is a good minimum these days for a complex scene, although I've used and grown and learned from Bryce at 64MB all the way to today's preposterous mass-RAM work conditions! Don't let RAM limit you, just create workarounds, and then remember how you WOULD have done it for later on, when you do have enough RAM? Good luck, hope this scene works out for you.