Harry,
we must always believe that it's bad technique on our part, because I know we can do anything if we put our mind to it!
I'm sure we can get some successful grafts going, if we brainstorm a bit more on this thread!
I never knew it was a challenge to graft lychee/longan, but it makes sense. I failed miserably with my best attempts, and have not ever seen one grafted in 8 yrs of looking at lychees in FL.
ps, I wonder if a small sheild bud method would work? using less scion material from the mother plant?