While other references refer to hemiola as any rhythm which goes against the basic background pulse (so eg stressing every 3 beats in a sequence of 4/4 to give a 3/4 feel over the background), Stone, with respect to my example above using the tie in 2 bars of 3/4 to get a 3/2 effect, specifically says: "This notation, however implies syncopations - a different concept from the original idea of merely "stretching" the regular 3 beats". References in classical guitar music that I've seen, always have referred to this stretching of 3/4 to 3/2. Stone also suggests "...since the modernization distorts the composers' intentions, a compromise is suggested:", being a rhythmic cue in 3/2 above the tied 3/4 notation.

(I personally wouldn't describe the opening of America as hemiola either - the alternation of 6/8 and 3/4 seems too strict to be a temporary effect).

Mick