+1
Yeohcheeweng,
1. You're trying to learn deep air diving on the internet. Not smart.
2. The guys above have outlined why, unless you're doing some bounce dive (which still has potential issues involving air that deep), at which you have zero experience, trying to do a dive to those depths on a single 80 is ill advised.
3. You have zero margin for error. Slinging another single 80 (assuming from your post that single 80s are your only option at this specific site) gives you at least some total volume that provides you with adequate gas for planning. But only if you understand how to plan the dive.
4. See #1 above.
Before you and your buddy head down to 60m - 197 fsw - on a single 80, please consider getting some additional training.
You really are gambling with your life trying to do air dives to that depth going off "what some guys told me on the internet".
Doc