On my mando, it doesnt seem to matter as much how I come down onto the grace note, as long as I come off of it to the side. Ive indicated on the ornamented version of The Coleraine where I like to add the snappy grace notes.
Always remember that indications of ornamental pick and placement are merely suggestions. Move your ornaments around. Let them come and go, lest they become hardened into an unchanging (and ultimately uninteresting) setting of a tune.
Youll notice that I dont indicate any grace notes in the chromatic passages in the second part of the tune. This is no accident. The tune itself in these passages is so perfect (in my humble opinion) that I wouldnt want to do anything to get in its way. Painting the lily and gilding the golden just because theres room for an ornament in a tune doesnt mean you need to stick one in there.
If youd like to try to add just one more kind of ornament, there are a couple of places where a pull-off triplet seems approriate and fun. The first comes at the end of bar four. Pick the E on the fourth beat; pick the F; pull off the F with the second finger; pull off the E with the first finger, and, if you like, pick the final D at the same instant that you pull off to the open string.
The last pick I find to come without thinking, since my right hand is indulging in the DOWN-up-down DOWN-up-down internal jig engine that helps me keep the emphases on the first and fourth beats of each bar.
The second place for a triplet ornament is the last half of bar six. The notes are an octave up from the last triplet, but you probably wont want to pick the last D (fifth fret, A string). Snapping down clean with the little finger will give you all the emphasis you need.
And, if your little finger resists its necessary role in this ornament, Id say that its that much more valuable an exercise for you, since the deeper you get into Irish and Scottish repertoire and the subtleties of style, the more youll need your little finger as a full partner and team player.
So, many happy ornaments and next time well leave jig time for an exotic trans-Mediterranean approach to thinking about Irish reels.