The Renown and Repulse really should have had 8 guns

The only reason that the Renown and Repulse ended up with 6 guns each was the number of guns and turrets that were readily available. The ships were large enough to have carried four turrets. They were almost 800 feet long, and had plenty of room. Their displacement was small, but quickly grew, as equipment and, eventually, armor was added. They represented Admiral Fisher's latest ideas as of late 1914. They had the Invincible armor basis, but with much greater speed. They also had the advantage of the latest anti-torpedo protection and outward-inclined armor. They were very leading edge. Admiral Fisher had hoped for 32 knots but they had to be pressed to almost 120,000 SHP to make that. They could more comfortably make 31 knots, which was still faster than any existing capital ship.