Hi
I need some advice.
I begin mCCR diving a few monthes ago, and used to dive with two 10L al BO tank, clipped on my left side. (a Nitrox 40 and a 20/35 or 13/70 depend on my planned max depth).
Now I begin to push the envelope

and I am limited with only two BO tanks. So I need to carry a third one. (to use a BO gas sequence like : 13/70, 20/30 and nitrox 40)
I suppose I will carry clipped by the neck snap bolt on the lower left D ring.
But, I have a doubt on tank choice : a composit carbon 12L tank or another 10L alu tank ?
What is CCR vet' choice in this case ?
Thanks in advance.