It's not required gearing - it's recommended! The ride says, "Minimum RECOMMENDED gearing is 39/27 OR WIMPIER".

I think they're just using that to give folks an idea of how steep the climbing is (looking at the pictures, it looks pretty tough!),with a bit of tongue in cheek humor. And, to head off the hundreds of 'what gearing should I use' emails the ride directors usually get!

You'll be fine!