Here’s an extremely easy way to calculate whether you are good with nickel. Divide the expected max continuous current by the cross sectional area of your thinnest point that is normal to the direction of current.
05A / mm^2 is overkill
10A / mm^2 is good
15A / mm^2 is okay
20A / mm^2 is bad
25A / mm^2 is awful
In the image below I am expecting 8x 20A through an area that is 65mm by 0.15mm, or 160A though a 9.75mm^2 area, or 16.4A / mm^2 which would be concidered an okay setup (this is a low power draw board since it’s only dual 6355 for light use which means it will be in the good range)
Edit: every weld is good for about 5A each, which means that top layer is good for 24x 5A or 120A total which is also fine