I like your target number, but I think that pushing for an Excelsior-a-year is straining our resource income, and could limit our ability to push out more hulls, which we need to actually catch important events, which is important since they are, apparently, miss-able. Even cutting down to every other year would free up enough resources to pad out the rest of the fleet nicely. The only reason I haven't been pushing it is because we don't have enough small slipways to actually do that kind of rapid expansion.
Actually, do we have more small slipways under construction? If we don't, we really need to get some going, because they're going to be a major bottleneck for churning out Escorts and Light Cruisers soon.