0.5 is half as tall.

This could be improved. What dBFS do yo get when setting yZoom to 0.5?

If dBFS are too confusing, it's probably better to remove the reference and say +/-1 instead.

If the audio file is properly engineered, you won't have positive dBFS at all (and, it's literally impossible to have positive dBFS in an integer-format audio file, because the maximum possible integer value for the bit depth maps onto 0 dBFS -- you might have values outside +/-1.0 in a floating-point file but it's not recommended to rely on that). So the question here doesn't entirely make sense.

Or should I use yZoom = 2 instead? Avoid the whole topic of out-of-range values.

I think you should stick with +/-1 instead of dBFS, and say that yZoom=2 will give you +/-0.5.

That works for me.

As an editorial aside, I find this last sort of comment -- a concrete suggestion for improvement -- to be very helpful. Otherwise, the PR author is left to guess what the desired improvement is, which only wastes everybody's time. (TBH I didn't know exactly what to do with the question about dBFS.)

You're right. I'll try to offer more concrete suggestions in the future.