water trials again today, the spray rails now permanently fixed again. It was a choppy windy day, so not the best of conditions, but I'm happy to say very little water ingress, and given the conditions, it has passed the test
Running with two 4 cell 2150 mah lipos, it ran for at least half hour with 3.8v per cell remaining, cold motors, so that was pleasing.
I tried more props, the 45mm "X" plastic props, these look horrible, but do give the best speed, a pair of brass counter rotating and a pair of brass 3 blade counter rotating, all form a spares box, so size and pitch is unknown. I tried them both turning outwards, and then inwards, the latter appeared to be best.
The "X" props do perform the best, so maybe the brass ones just for show!