I have not used that battery but it is a good 20 CDR (continuous discharge rating) battery.
Everyone is free to set their own parameters (with regards to headroom), and I can only say what mine are.
I try to never exceed 50% of the CDR of a battery. So with a 20A battery, that would be 10A.
This
Ohm's Law Calculator tells me that a 0.4Ω build is as low as I would want to use.
The reason that I place a 50% limit is because as a battery ages the mAh of the battery degrades, as the mAh degrades ... so does the batteries c rating (amp limit). So down the road, a 20A battery may only be a 10A battery.