The Mk III Boat
While the design of the MkII boat may have become fixed, developments continued and the MkIII boat was introduced. The earliest examples seem to have appeared in 1976. Two major changes appear in the new model. The first is that the saloon's sliding wheelhouse is replaced with a fixed head that incorporates a sliding roof panel. The second is that the foredeck becomes a well with access via a door from the saloon. The well incorporates a semi-circular aft-facing seat running around the bows.
Without the sliding wheelhouse that has to surround the main part of the cabin the MkIII has superstructure that appears marginally lower and a certainly a few inches narrower across the top of the cabin than the earlier boat and that provides can give some extra clearance at the lowest bridges bridges on the Broads. In spite of that it appears both types were reckoned to have the same 6'6" air draft on the notices requiring hirers to engage the Bridge Pilot at Potter Heigham.
It's worth reflecting on the origins of the new version. F.B. Wilds yard, at Horning, had introduced its iconic six-berth Caribbean class cruiser into its hire fleet in 1966. This was the first design to have a well forward in a boat with a single level cabin and its steering position in the bow. Larger and smaller versions had followed. As the general design proved exceedingly popular with hirers other builders began producing their own designs with similar features.
You could say that Alec was forced to follow the trend with the MkIII Safari. Some argue that while a forward well works with the 12ft beam of the original Caribbean class craft, it really struggles in a 9'6" beam boat as there's barely enough room for three pairs of feet to be placed on the floor.
Having a door in the centre of the saloon produces problems internally as well. The door occupies the space where the extending bed in a four berth boat needs support. In part this accounts for why no two examples you encounter, will have the same style of door, reflecting the fact that builders each have developed their own solution.
In a three berth boat a single door can swing inwards without issue. However, in four berth boats the door is often made to swing outwards, and that sweeps almost the entire floor area of the well making the well almost unusable as seating. In others double doors are fitted. While that keeps the well usable for seating, it adds considerably to the framing making forward vision for those on board is much restricted.
Owners, however, tend to argue that the chief benefit of the MkIII over the MkII is that the forward well provides much better access to the bow when mooring and rather than thinking of the semi-circular bench as a seat, they treat it as a step. It's also argued that it is safer to drop a mud weight over thew bows from the step in the well than from the foredeck of the earlier boats
Another significant benefit, it is argued, is that it solves the problem of getting a reliable seal between the wheelhouse and windscreen. Various solutions have been shared amongst owners of MkII boats to overcome that problem, but it is probably no worse for than those with twin bow doors on a four berth MkIII boat.