Aarg!
One of my favourite options.
Thanks for checking, I wish I had tested this a little bit earlier. Now, i am running out of time.
Related to my "negative" experiences with CBsubs conditional display, I also tried the Incubator plugin "Conditional" to hide the whole "Subscription" Tab. Thats not my actual goal, but i wanted to test if the Javascript stuff works on that page at all...
I could hide/show different fields, but not the subscription tab?! Maybe this is of interest for you as well.