Charge controllers:
Boost to 28.8V
Float to 27.2V
Smartshunt:
Charged voltage to 28.6V
Tail current: 5% (62.1A)
The goal is to have the smartshunt hit 100% around 30 minutes before float is achieved.
If you're not getting to float, you have insufficient solar for your loads.
This may be iterative.
Are you running a Valence compatible BMS?
Are you checking that the 2X 12V have highly similar voltages at all times?