II was going to ask for 25%, though 50% or 75% would be helpful too. 90% gives only 10% leeway in terms of knowing when to advance. If I'm gigging and need both chords and lyrics, that gives very little room for error and I need to be staring down at the screen to make sure I don't advance too early.
I guess what I'm really asking for (like cajoler) is a way to increase the amount of scroll to more than a line at a time.