Originally Posted by Malcolm H

You need to use a digital angle meter like eFlight AnglePro ll or Wixey digital angle meter. The Wixey has a large enough base to be attached to the surface with small pieces of double sided tape (reduce the stickiness by rubbing it first so you don’t pull your paint off). The AnglePro needs a mount to hold it steady. CK Aero sell a suitable mount.

Which ever meter you use, always place it the same way round on each surface to increase accuracy.

Malcolm