Quick little test comparing 6:1, 12:1, and 18:1... I wanted to see how noticeable the differences would be at the delivery stage (generally compressed and 1080p, not 4k/RAW). Figured there would be some soon-to-be-Scarlet owners (or 32gig SSD owners) that would want to check it out in order to maximize their REDmags. I cover most of the details in the video's description.
Must say I was pleasantly surprised seeing as how we're dealing with approximately ~3gigs/min vs. ~2gigs/min vs. ~1gig/min... Holds up extremely well in the grade, too. Granted there was tons of ambient ~5600k light, which definitely helps, but it's good to see that you aren't sacrificing too much quality whilst literally getting 3x the amount of recording time out of the same REDmag. It certainly doesn't seem to be 1/3rd the quality at the deliverable end (they all look pretty much the same, which I guess is to be expected when they end up being crammed into the same 10mbit h264 codec regardless of the source ratio, but still).