Unless you want be replacing bearings more often and getting more noise
and vibration, bearing length should be kept as it is. Gap from aft end of bearing to prop should be kept to a minimum for the same reason. (shaft OD is OK)
Fora soft mounted drive our worse case movement and clearance is 9.00mm forward movement and leave a 3.0mm gap for water
to exit bearing. So make sure you have 12.00mm gap.
anode might be the best option.