Note that the record for absolute highest manned single propeller-driven aircraft is still held by Mario Pezzi who flew to 56050 ft in a Caproni Ca.161 in 1938. The Grob Strato 2C flew even higher in 1995 but it had 6 m diameter propellers, wingspan almost as wide as a 747, and not just turbos but full jet engines as "gas generators" to feed the manifolds of the piston engine pusher props. And the Grob G 520 went up to 53573 ft but it's a turboprop rather than a piston engine. Finally, the Perlan 2 when up to 76124 ft. with no motor at all.
Note that the record for absolute highest manned single propeller-driven aircraft is still held by Mario Pezzi who flew to 56050 ft in a Caproni Ca.161 in 1938. The Grob Strato 2C flew even higher in 1995 but it had 6 m diameter propellers, wingspan almost as wide as a 747, and not just turbos but full jet engines as "gas generators" to feed the manifolds of the piston engine pusher props. And the Grob G 520 went up to 53573 ft but it's a turboprop rather than a piston engine. Finally, the Perlan 2 when up to 76124 ft. with no motor at all.