Thanks for that Rory. I was doing exactly the same, but instead of using an example I was using the default template used when you do "New Cabbage...->Effect".
The gain rslider did not work with that code and I went mad looking for the cause of that. Finally, it's because in that template the rslider doesn't have its range attribute defined!
Do you know when you'll have a new beta released? I'd like to try my oscillator bank with the newest changes introduced in the develop branch. I have Windows 32-bit in an old notebook and I could try OSX on Friday. BTW, fftdisplay is an excellent idea! I saw a glimpse of it when I cloned the repo yesterday.