The one you show is the on-deck naval mount (later also used in certain batteries).
No, I mean that one:
That type of shield was most common in coastal positions. It theone that was later "upgraded" to the Devil's Gap version. The original shiled is still there:
Probably the best way to re-create the shield is to build first the original casemate-type shield and then attach the add-on shield, just as done in reality.