Intresting... I am going to take appart my sons UE-8 and inspect the cups - It was converted from a cottered crank - I'll see if there is any evidence of the balls not running in the races or cups properly - But I did not have any problems using the 5s-b spindle with 54mm between the races on that bike so even though it was an old bike with a cottered crank it may have not have had extremely thin cups - I don't remember if they were Stronglight cups or not...