While we indulge in starry-eyed speculation about how much to expand the SoL, how about a single tier Roker End going a long way back, like the new White Hart Lane? If 'safe standing' ever came in, it might evoke memories of Roker Park, re-creating the passion and carnage of a by-gone age.The upper tier can go all the way around to take the SOL to approx 65,000 at relatively cheap costs per seat.
However I have it on good authority that there is a possible option to add a further tier on top of the West Stand that could add 10,000. Costs would be more though