SPIT MK I/II and over boost

[Crumpp]

Obviously the pilot can choose to climb at constant IAS if aircraft capability permits

Climb speed refers specifically to Vx or Vy. It is not common to split hairs on it having it mean anything but Vx or Vy without specifying the condition of flight.

http://www.experimentalaircraft.info...imb-speeds.php

All aircraft can climb at a constant IAS. If you do that however, you are not at Vx or Vy.