Jerry O’Sullivan gave us a few good points on backstitching at the Pipers’ Gathering.
Firstly the rhythm: LONG-short-short-LONG was what he used.
Secondly, he used two techniques - Left hand and right hand. When playing a note with the left hand (the LONG notes in the rhythm) - for instance back d, C#, B or A - the stitch notes were G and F#. When playing a right handed note (G, F# or E), the stitch notes were C# and A.
Putting it all together and using the LONG-short-short-LONG rhythm this gave a tidy little exercise descending the scale from back d to E :
(Upper hand)
d-G-F#-d
C#-G-F#-C#
B-G-F#-B
A-G-F#-A
(Lower hand)
G-C#-A-G
F#-C#-A-F#
E-C#-A-E
Jerry finished with a cran on hard bottom D but also using the back-stitch notes:
D-C#-D-A-D
He had a few interesting variations which were completely lost on me. I was struggling to write it all down and he can play faster than I can think. I must buy a dictaphone.