Welcome aboard Matthew. Let us all know when the book/record is ready I think you have a number of customers ready to buy as soon as the print is dry.
Following this thread I took another dip in to A.L..Lloyd's book Folk Songs in England originally published by Lawrence and Wishart Ltd, London 1967 he devotes a section to the history of the shanty. Unfortunately I do not know whether the book is still in print but if you can find a copy it is an excellent read.
His view is that the "practice of shanty singing as we know it best emerged during the American dominated packet ship days of roughly 1830-50 and it reached it's peak in the British dominated clipper ship era of 1855-70"
These vessels were commercial craft with tight sailing schedules. As a consequence of the Industrial Revolution in Britain and world wide demand for machine made goods Isaac Wright and Co's Black Ball Line for example, began their regular run between Liverpool and New York in 1816 sailing on the first of each month regardless of the weather or the amount of cargo on board.
Lloyd goes on to point out the importance of the shanty man. Competition between these packet ships and other such commercial craft meant that the shipowners would try anything that might help the fast and efficient working of their vessels. He says "men heaved and hauled better if they sang at work. 'A good shantyman's worth six more hands on the rope' was the saying. Some companies paid a bonus to the man who was a good leader of work songs, the man with a strong voice and a ready wit for spinning chants out of his head in a way that had his workmates toiling with a will."
I believe on war ships as opposed to merchant ships there was a rule requiring silence on deck which seems reasonable. If you were stealing up on the enemy fleet in the mist with a view to taking them by surprise a hearty rendering of Haul Away Joe by the lusty matelots wouldn't help.
Hmm I don't suppose in today's world Stealth aircraft crew are encouraged to sing "Coming in on a Wing and a Prayer" as they go about their business. Though it might give any ground tracking station something to puzzle about - "Er we can't see it but there seems to be some singing coming from somewhere - good chorus!"