Hi Les
9/8s unlike most of the the other trad dance tunes are not symetrical round the middle of the bar, this means that the stress points of the bar can be 1,4,8 but also 1,4, or 1,8,. A lot of slip jigs came from 3/2 hornpipes which have a similar asymetrical phrase structure, for example "Dance to thi Daddy" 1234, 56, emphasis on 1 and 5.
Slip jig are oftern phrased in note lengths like this
1/4 1/8, 1/8 1/8 1/8, 1/8 1/8 1/8
or
1/8 1/8 1/8, 1/8 1/8 1/8, 1/4 1/8
but all the other possibilities occur as well.
An interesting technique used in some 9/8s from the North East Tradition is to phrase the tune as if it were 6 bars of 6/8,
1/4=2 1/8=1
|2 1, 111, 2 1 | 111, 2 1, 111 | and so on.
Rhythmic ambiguety is quit common in tunes from the NE. A good example is "Kissed Her Under The Coverlet", which does not appear to on JC's Tune finder, so I'll try and post an ABC of it.

All the best

PP