You might also want to consider what happens when you select reverse (assuming your boat does this). In my early days I nearly ruined a nice propeller by not allowing for the fact that when the propeller pulls backwards it tries to pull the UJ apart. If there is space in the system, one or both brass inserts will be pulled partially or completely out of the red plastic bit, and the prop might hit the rudder. The way to avoid this is to install a collar and washer on the shaft next to the inboard end of the prop tube so that the collar takes the astern thrust not the UJ, Hope that all makes sense.
Greg