How envious I am about your start !!! 
One sure thing is that when I plug a SuperB battery as supply (with Anderson park connector), the engine revs 50rpm more and the engine fires instantly
I do have a LiFePO4 battery, for sure it could help with the startup.
UPDATE 
With 24-2 toothed crank wheel, no more cranking issue. Engine starts instantly, cranking count is good.
With a little Lithium battery so with less cranking rev than SuperB.