I see what you mean N1KK0 about using one spacer on the end of the crank will cause the hub to move upwards if there is not a matching spacer above the hub ,the only other way would be to bolt the blade plate to the hub with 3 bolts and nuts but you would need to drill the blade plate and washer and hub. 1/4 inch UNF high tensile bolts would work.
I can see drilling 3 holes being quicker than making the extra spacer as long as the hub and blade plate are not hardened. The problem with having 2 spacers is the one on top of the hub will need to be a snug fit on the crankshaft so may take a while to make.
I would normally grab another hub from another mower and use a different blade plate if I had one that was suitable otherwise it can be a little fiddly .
