I have ben trying to think outside the box regarding planting 2 young fig trees.
My soil is very shallow, thin and quick draining. I am physically unable to dig a deep hole but have access to an old water tank. Approximately 6ft by 4ft in size, it never has more than 2/3 ins of water in the bottom, no matter how much it rains, so I wondered whether, if I put rubble in the bottom to a depth of 3/4 ins., and then filled it with compost, it would make a suitable home for the figs.
I have seen figs growing in timber 4 'by4' containers in the garden at Heligan. I have a south facing spot where I could have the water tank put.