All commercially available "SLA replacement" LiFePO4 batteries have overcharge and over-discharge protection.
From my experience, if run in parallel they will have the same voltage. After a typical 5-hour flight with a full panel running, about 12V.
Charging two similarly discharged batteries in parallel worked well, but the chargers I was using at the time didn't quite have the voltage required for LiFePO4. I now use separate chargers that came with the batteries from Tenergy.
But underneath the workbench the glider batteries charge on, there's a bank of eight AGM batteries running the inverter/UPS on the entire house. They're running at 48V in series/parallel, under constant charge and discharge.
Adding a diode to your batteries will prevent your Strobl Solar system from charging them in flight. Discovered the solar panels unnecessary with LiFePO4.
Jim