Some 3/2 hornpipes seem to have alternating bars in 3/2 and 6/4 even if they are written as 3/2 tunes throughout.

The Folkworks Session Collection includes the example of Rusty Gully which is actually written in the 19th Century William Vickers collection with alternating bars in 3/4 and 6/8 (all note values halved). The Old Lancashire Hornpipe which Spiers and Boden have recorded also seems to follow this pattern with an opening half bar in 6/4 followed by 3/2 6/4 etc with a closing half bar of 6/4 in each section.

Playing the tunes in this way gives them a definite rhythmic lift.

OTOH, The Lads of Alnwick works best played as 3/2 throughout.

It would be interesting if anyone were able to recover dances that were danced to these tunes as it would tell us a lot more about how they should be played.