Interesting video but personally I think you are better off with 4 x AA LSD NiMh rechargeable batteries that will give good runtime and don’t require any mods to the radio at all and you can still replace the NiMh with 4 x standard AA batteries if you inadvertently get caught with a flat battery when sailing.
Experience has shown that decent NiMh AA cells will significantly outlast LiFe batteries when looked at whole of life use.