That said, 25% speed at the low resolution setting is relatively fast, and you should expect to see some wiggling of the lines, regardless of the pen height. We normally only use this kind of speed or faster with broad felt-tip pens. There is always a tradeoff between speed and precision– you may prefer to go slower for higher quality.  Another thing to consider, if only long strokes are causing problems, is to use the “constant speed” option, which turns off the acceleration. That will slow down the speed on long paths, and move faster on short paths, in comparison with the default behavior.