Sizing a battery according to an existing solar panel (and not the opposite!)
You actually want to oversize even more than that. Here are some points to consider:


Lithium-based batteries have shorter lifespan with 100% depth of discharge.  If you want your installation to work for >10 years, it's recommended to keep cell in their comfortable voltage range (3.0 ~ 3.3 V), without ever going as low as 2.5 or as high as 3.65V. This means you will be using about 80% of their capacity.
Even in the best conditions, you should expect available capacity to decline. Depending on the quality of cells, you'll end up with 80% of original capacity in 10-20 years, assuming 1 charge cycle per day.


So, if you need 60Ah of useful capacity in your system 10-20 years from now, you should aim at 60/(80% * 80%), or at least 93Ah of raw capacity. That's how I would size it.