The UK continental shelf only goes so far north because Shetland is here. In an world with an independant Shetland the UK continental shelf would stop half way between Shetland and Orkney making Fair Isle fairly important Of course if Orkney came with us the area would be larger. In a post devolution world Shetland will have control over the EEZ out to 200mi or the half way point to the next teritory, as described in the UN UNCLOS treaty. https://en.wikipedia.org/wiki/United_Nations_Convention_on_the_Law_of_the_Sea. The figures posted showing the (nearly) current net contribution to the UK economy is just showing the baseline of what is possible i.e. we can go independant and balance the books at the very least. Post independance there will be oil revenue at some level, Income tax on offshore workers in the Shetland EEZ, Increased income from benifits that would come to the Shetland FIshing industry with control of our own waters, and if we take the example of other similar island states, incentives for attracting additional business to the isles through lower corporation tax etc.