I think the RN did not consider the Stonewall a threat, they knew that it's timber construction and thin armour wouldn't stand up to a true ironclad. The accepted battle range for the RN in 1860 was 800 yards, and this slowly crept up to 1,000 yards. There was a better chance of getting hits with broadside ships mounting numbers of medium calibre guns, but the ever bigger gun and ever thicker armour mantra had taken hold in all navies, blithely ignoring the lesser chance of hitting with fewer slower firing guns.
The best of the MLR was the 9" Armstrong/Woolwich MLR - more by accident than design. Having said that, at Alexandria, American observers were surprised at how accurate HMS Inflexible's 16" MLR were compared to other vessels.
In terms of fire control, Captain Cochrane in HMS Warrior had the broadsides "slaved" to the centre gun. You can see the deflection scales on the gunports in her at Portsmouth. HMS Terror, with Admiral Milne on the NA&WI station had the same system but centred on two towers, one on each broadside.
My reference was to the RN's reaction to the French ironclads. The threat posed to the unarmored RN vessels & to commerce was very real.
Of course the Stonewall / Azuma was constructed of wood & iron plate. The entire ironclad U.S. Civil War compliment was constructed in that manner.
It is instructive to note that the resistance of wood was exploited by the pocket battleship Bismarck. It had a layer of wood in its torpedo belt.
The difficulty inherent in laying 1,000 (+) yard rifles from the deck of a ship was not a unique to the RN. At Manila Bay the U.S. Navy scored (+/-) 10% hits against Spanish navy vessels.
The best description of the vexing challenges of laying naval guns that I know of is in Robert K. Massie's "Dreadnaught, Britain, Germany & the coming of the Great War."
Large caliber RN ordinance was laid, in part, by peering down the bore. Each gun was laid by the gunner.
The concentration of fire & deck marking referred to were initially utilized by HMS Shannon during the War of 1812.
I can attest from personal experience that after a couple of rounds you can't see a thing from the gun deck. No matter how improbable your shipmates.
The same is true on land.
At Alexandria in 1882 the RN Mediterranean Fleet (if memory serves) fired (+/-) 2,000 rounds at Egyptian forts over a ten hour period while at anchor. The small number of hits were very effective, the rest were described as having been "…fired wildly."
It was Admiral Jacky Fisher & Admiral Scott who overcame dogged resistance to establish the efficiency of remote control gun laying from high atop the smoke.
In a harbinger of things to come, General Sherman & Admiral Porter issued a code for controlling the fire of gunboats with signal flag or torch.
At Baton Rouge LA a signalist in a church steeple rained large caliber shells down on shocked CSA attackers. F-L-R or F-L-L, fire a little to the right, fire a little to the left, e.g., was a simple , effective indirect fire control system. Wisely, the CSA attackers broke into a howling retreat.
Bringing the