I picked up an old Ergo 46 with a Thunder Tiger 46 which would run on 10% Nitro and had a flight time of 14 to 18 minutes. It was the only helicopter that I ever owned that was almost a true hands off helicopter. We timed it a it would stay in a hover in one spot for 30 to 45 second before you had to make a correction.
Autos were a dream, it did have the stretched boom and 600 mm blades.
The engine was not a power house but once I got all the bugs worked out and discovered the engine didn't like high Nitro it was dependable, started on the first hit and always ran perfectly.