The devel module has setting where you can see how much memory PHP is using for page loads. Right now the UberInstaller doesn't do any checking how much memory PHP is allowed to used. When I start work on UberInstaller 2 in the near future I'll be adding a check for memory_limit. I think I'm going to try out a test install and enable the minimum amount of modules and the maximum amount of modules to get a low to high end amount of memory that you'll need for Ubercart.