Yeah, we normally train pilots to use the throttle as a slide bar and not as an on-off switch.

If you really want to fly good aerobatics and get reasonable flight duration, try this:

Take off at full, reduce to slightly over half, trim it out.. no roll no climb or descend, just straight and level flight with "hands-off" the transmitter. Emphasize - it should fly straight and level.

The trim should be set for that type of flight. Then aerobatic maneuvers returning to that throttle setting. You should easily exceed 10 minutes full tank of fuel with that OS 55 AX.

CGr.