Have a look at the attached file - it summarises the method I used to rebuild my Dragonfly crank. That crank has now done about 30,000 miles and is as good as the day I fitted it. Most of the commercially rebuilt cranks with thin wall liners fitted into the conrods that I have seen, have had seriously short working lives due to the liners being too thin and flexing, resulting in the surface of the liners breaking up. If you go down the route I took, I would suggest it would be a good idea to halve the number of oil holes in each big end journal (to ensure the oil gets divided equally between the 2 big ends) - worn Dragonfly cranks throw most of the oil out of the front big end, and starve the rear.
Hope some of this helps,
Regards,
Eddie.