Ahh our experimentation was a lot more rudimentary to make paper .
We mainly dabbled in the banana fibre and I do remember my partners, a while back, worked with someone for a test piece of a bio-plastic with about 5% banana fibre and 95% corn starch. It looked nice but it wasn't very viable, and more concentration of banana fibre was unfeasible (I can't remember the reason)
@JasperB I am not sure how it works with the banana peel (the only thing I think we played around with this was making dyes for shirts) but my reckoning is that the stem allows you to separate the constituent parts of liquid, pulp, and fibre more effectively to work around with than the peel, which is a lot more mushy / mixed and harder to separate out, could be why it does not form in a cleaner manner. That's about all that I've got to contribute I'm afraid