To be honest I'd probably wire 24 over 20, for something like Blue, or Pink (in my case).
I found that wiring up 12 was much simpler than the other ones I did, because it was a multiple of 3 (the number of LED's I had in the circuit) and 4 (the number of sides on the fan). This might sound obvious, but it makes it much simpler, as you don't have to wire over any fan corners or anything like that. Don't get me wrong it's not the hardest thing in the world, but I found the 12 one of the easier ones I did
kd