So I'm poking around on the VII today fussing with the shaper fence that I just discovered is specific to that machine (doh!), and I noticed that the front boss on the table carriage has a threaded hole. I pulled a short screw, normally used for securing the dust chute for the drum sander, and popped it in. These screws have a little nylock embedded in the thread, and can be set for a certain tension. Viola, a carriage-height drag setting! I haven't seen anything about this in the manual.
The early VII has a combination crank and fliplock for carriage height, but usually requires two hands and some patience to set just right. With this little drag screw I can set it tighter for finer or loose for faster movement. I added a little disc of rubberized-paper gasket material to prevent it buggering up the table tube. I'm thinking about adding this feature to the 510 as well.
Here you can see the carriage height lock is completely disengaged.