I’ve written before about how to change the auto scrolling speed/length in Dragon 11 using the Mouse settings in the Control Panel. However, if you only use auto scrolling for reading pages in Firefox, there’s an add-on that does the same thing and isn’t as choppy: Yet Another Smooth Scrolling, which works with Firefox 9.
YASS deals with the scroll wheel and the arrow keys, both of which Dragon can handle since its auto scrolling is just repeated turns of the scroll wheel. In the main settings, you can adjust the step size, smoothness, and acceleration. Under the more advanced options, you can set which keys you want to perform smooth scrolling: Arrows, Page Up/Down, and Home/End. All of these can be selected at once. There is also a blacklist, where you can put websites you don’t need smooth scrolling in.
The default step size is about 60, which is something like three lines (though I don’t know if that has anything to do with the mouse wheel settings in the Control Panel). When I say “start scrolling down,” there is no jerky pause between scrolls the way there was without the add-on. (Without the add-on, Dragon’s auto scrolling was a little bit choppy even though I had checked “use smooth scrolling” under the Firefox options.) It’s much easier on my eyes.
Be aware, however, that your step size will also affect your arrow keys if you choose. This means that if you say “go down two,” for instance, you will potentially go down farther than two lines. However, if you only use it for the scroll wheel, it should make auto scrolling in Firefox much easier.
Note: Unfortunately, even with this add-on, saying “scroll up/down” will still take you to the very top or very bottom of the page. You’re still better off speaking the Space or Page Up/Down keys.