Sad that there are only 2 left flying. They were pieces of deadly art that have to be seen to be appreciated.

The hard part- and mostly a highly expensive one are the Props. I believe they need to be balanced like a Medieval sword when made. Plus the engines and such are difficult to replace. Parts for some planes of that Era are sometimes either foraged or newly forged / made. An Art that is slowly dying out.
Any imbalance in the blades of the propellers will throw the the plane into the shakes . Let alone rip the engine from the plane causing structural damage and loss of the plane.

Good afternoon Maj Kim Patterson. Excellent post. Thank You for sharing this.