It's my first year doing this event. How do you make sure you have all the right and sufficient info without overflowing the binder? Often times, I'm afraid scant info will cost me questions at competitions, but concurrently, aggregating too much info on a species might be an obstruction to time in regards to navigation.
I'd recommend a font size of around 8 pt and using similar condensation methods as you would for notesheets (abbreviations, choppy sentences, etc.); you can probably get down to about half a page per species, which is pretty decent for navigation once you're familiar with your binder.
From my experience with my binder, the best way to navigate easily, is of course, knowing your binder super well, and have a very uniform organization for all your species, so you know what information is kept where. Use bullet points, not paragraphs (well, paragraphs don't really work with me, they might be your thing though). My binder is quite overflowing.....six inches thick.....but she's done me well and there hasn't been a time in which I can't find any information due to poor organization. The only issue with such a thick binder would be flipping the pages, but it gets easier with page protectors (page protectors are probs 2/3 of the thickness XD). At the competition, my partner and I usually don't even flip the pages, just turn it so that we can read the text.