The Merlin hull is a cut down Sparrowhawk, but it is too deep and wide so tips from side to side at rest. Also it isn't 5m more like 4.8m. the extra length of the Sparrowhawk whilst still slightly tippy (compared to later desings) is far more stable at rest.
Under way the Merlin runs bow up even with the engine trimmed in and needs careful distribution of weight up the sharp end. Osprey stopped making them in 92 because the Sparrowhawk was much better whilst costing little more to produce.
I part exchanged my Merlin for a Sparrowhawk and there was a big difference.
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