Hi Jimmy,
i fitted my engine & box last week & know what you are saying as i thought the same...............but a fellow kitcar owner/mate came to look at my build & i asked him the same sort of question......
he said that once the propshaft is bolted in place it should reduce the movement at that end of the gearbox.
i,m not sure if this is true but it seems logical i suppose.
cheers
andy
ps thats why i wear a cap...... the hair photo