Sipper, are we talking about the Flavilinea, which is a smaller species of the genus.
Ok, there are a number of species that emerge as winged duns, unlike others that go through the transformation in the meniscus.
And as you noticed they do not remain on the surface for long.
I do find it strange that the trout act in the way you describe all be it not a unusual characteristic.
Is the water slow flowing and a flat glide surface or is it more a popply water surface.
Also the position of the trout, is the fish for example just off of the main feeding line in slow soft water and then turning out into the main stream where it sees the duns ?
Often the nature of the water surface movement is related to fish feeding behaviour, or how they see the fly.
Either way there is no reason why you should not be able to catch these fish with dry/emerger soft hackles, and nymphs, if the fly is right and you present it the way the fish wish to see it.
Often as not before a hatch fish are taking the nymphs at the stream bed, when the hatch takes place they will then turn attention to the surface.
John, l do not think that height is so much the issue here so far as rod length its simply what a longer rod will enable for you to do and for many reasons.