I am pro 10 units. I never understood the appeal in keeping 12 units when ultimately 10 of them count (I think 11 is ok), it just means you're working harder and gaining like nothing in return, in fact you could be losing because if you're already not doing well in some subjects, then you can't fully dedicate your attention towards them bcz of those extra units, you could even burn out quicker since you have more workload but that depends on you as a student. personally I don't think a safety net is necessary if you consistently try to up and maintain your game in 10 units