Nice work Mick - that is a great article, first time I have read it.
I had a similiar problem on my z1000 at the end of the 2001 season - it was jumping pretty badly out of 2nd and 3rd. Cut a long story short ( and no piccies

), split cases, check out 3rd gear on input shaft, dogs all worn to buggery, I had also worn the selector fork down to about 3mm, min. thickness according to the Gospel of St Factory Manual was 4.5mm

no wonder the mongrel was jumping out of gear !! Also the groove on the input shaft was out to about 7mm !! ( should have been about 5.....)
did a plunder from a spare z motor, with a gearbox in much better nick, no more problems

bloody gearboxes.....
cheers
GyroGearlooseDave