I recommend you do not
adjust the up/down lines. The down slack is removed when the rudder is cleated, but is needed when raising the rudder. On the other hand, you should remove slack for left/right control when the rudder is down, locked and centered, but that's another matter.
There is a natural variation in ease of rudder lock-up because of slight thermal differences in the mold release process for the rudder blade and rudder housing. That's why the cleat is always recommended.
Some rudders can be difficult to lock/unlock, also due to this variation. When dropping the rudder in this circumstance, you can manually tension the rudder down line, gain a little speed, and swing the rudder left and right to lock in place, then cleat. That same rudder can be hard to unlock -- if so, reverse the procedure: pull on the up line while swinging the rudder control left to right (the lateral water pressure aids the process).