After removing the fiddly connector box screws on the fron of the dynamo, hanging upside down under the canonpy to disconnect the concealed voltage regulator, removing the countless tiny nuts and bolts from the canopy supports, then removing all but inaccessible dynamo hold down nuts and then removing the dynamo base from the smoke box extension, hand filing the slots (I have no milling machine) the replacing all the above and finally re-touching the paintwork inevitably chipped during removal.
I reckon a new belt is a bargain