Based our extensive testing, turning "Black Overprint" off works for some files. The biggest issue is when you set Text Quality at high and go into Impose. When you go into Impose, sometimes the output size changes from printing at 100%. I suspect that it's the FieryOptimized2.joboptions settings (your file gets converted to PDF when you go into Impose) and have suggested that to the EFI guys. This problem only shows up for some files (can't narrow down to specific RIP settings, file types etc) and because of that, our default setting for Text Quality is set to Normal, which is a shame...