Too bad we've gone backwards over all these years. My production 1967 Bell 47G-3B-1 with the standard piston Lycoming TVO-435 will hover above the service ceiling of many of those in the video. HIGE at 16,000 ft. density altitude at 2950 lbs max gross, and when a bit lighter at 2650 lbs, HIGE over 17,000 ft. density altitude and HOGE 16,000 ft, (all according to the manual; I have personally done HIGE it at 13,000 ft. d.a.).