Bloggs,
In practicality, I doubt you'd ever be able to have the calculative ability at hand to adjust your IAS to achieve a better angle. Fly Vx as published would almost always be the safest solution (though, of course, how many light aircraft pilots actuaaly know their current Vx for their actual weight?)
As has been pointed out, gliders, with their much larger ranges of L/D and quest for ultimate efficiency DO make alowences to achieve best glide range adjusted for wind, which is roughly analogous (and, as I write, I realise that speeding up in a headwind to achieve best rang in a powered aircraft is basically the same princliple) and a gps linked glide computer will supply the best speed to fly.