I have now tried two of them. I got some small Caribbean bananas so I tried out the flax seed and banana crackers and the oat and banana cookies.
The crackers I got the best result by cooking for 45 mins (although I probably did not press down the mixture enough) and if I had they would have had a harder shell in less time.
The cookies turned out well in the 15 minutes recommended, as an experiment I gave some an extra 5 minutes which made them more of a biscuit texture. I didn't add anything to them, they turn out quite sweet so I'd be wary of adding to many chocolate chips or raisins as extras. 