Matrix RAID 2x320Gb: How should I balance RAID1:RAID0?

So currently I have 2 320Gb 7200.9's in the Matrix. The issue is I think I made a mistake. I Currently have the drives split at 150 RAID1: 300 RAID0. This was due to the fact that I wanted to have more total capacity for files (ie. 450Gb), but I am doubting the decision more and more as I realize that most is not all of my data should be redundant. I've created a graph that represents this relation and shows the effect of modifying the ratio. For simplicity's sake, it's based on 2x300Gb which is close enough to 2x320. Also this can be applied to any scale, because only the ratios are of importance.

I think column 2 has a good mix, but compare the total capacity to say column 9, and you can see how much space you lose to redundancy. My current choice (column 6) when stacked up against the others appears to be a sweet spot between total capacity and total redundancy. Which would/have you choose/chosen and why?

I should have coloured RAID0 red, and RAID1 blue , so the colours are inversely representative to their true safety.