Calculation
I have just been able to show that, regardless of flap position, the very early stage of the climb using 56 KIAS will place the aircraft at a higher height than using 62 KIAS. This is simply because the aircraft leaves the ground earlier.
However, the point about the Vx using a flap clean config versus the 56 KIAS Flap 10 speed is a clincher.
Thanks to all for a swift response.