The commercial pilot and pilot-rated passenger departed on a local flight with the intention of performing aerobatic maneuvers.
According to a witness near the accident site in Fairmont, Oklahoma, the Skybolt 300 flew over at a high altitude and performed a barrel roll. It continued south and then pitched up to climb straight up. The nose of the airplane came down through the horizon and the airplane started “tumbling.”
He said that about 1/3 of the way through the tumble the airplane rolled over on its back and entered an inverted flat spin.
Damage to the airplane and witness marks on the ground were consistent with the airplane hitting the ground in an inverted, nose low attitude. Both souls aboard died in the crash.
The witness did not see the final seconds of the flight and it is unknown if or when the pilot may have initiated a recovery from the intentional maneuver. It is likely that the pilot waited too long to recover from the aerobatic maneuver.
Probable cause: The pilot’s delay in recovering from an aerobatic maneuver, resulting in collision with terrain.
NTSB Identification: CEN16FA278
This July 2016 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.

I know it may be a nitpicky thing but the tradition of using the Souls is really a term that needs to be retired I saw a checklist form the other day that used the term POB (people on board) I believe if memory serves me it at one time listed SOB (souls onboard) souls is a leftover it seems from nautical days, so only their souls were on board? what about their body? I know, just being a smart a__ but a strange leftover tradition that IMHOP needs to go away
CG checks are important prior to flying aerobatics in any aircraft. Inverted flat spins are not easy to recognize initially. One must try to get the nose to break thru the horizon and point upward toward the ground. Then accelerate for speed and recover once the plane starts flying again. Or, roll back to upright position and recover from a normal spin in standard recovery methods.