Which airline are you flying with?

So it should be ok as long as you don't cram it full!http://www.lufthansa.com/uk/en/Carry-on-baggage on there it says Dimensions for carry-on baggage: 55 x 40 x 23 cm
Flipside 400 AW is; 30.3 x 25.3 x 46
You should be fine.
So it should be ok as long as you don't cram it full!
That's a crucially important question. Their policies regarding carry-on baggage vary more than you might expect.Which airline are you flying with?