Hi Hamish
you wont regret the larger motor.? I have got a 3.6 hp on the Duo 480 and at times? (up wind in a strong choppy sea against the tide) I have been glad of it.
These small multis get a lot of windage on the superstructure.? In calm conditions any tiny egg beater would push the boat.
Waiting with great anticipation for a sailing report
regards
Bryan