My shed is 2.7m sloping to 2.4m and when working in the back of the rangie, I am constantly hitting my head on the beams.

My advice is stand on the back bumper of your landy and measure from the floor to your head, add a bit and that is the minimum height you should have.

AFTER I built mine, the shed builder said it would have cost bugger all to go a bit higher.

Good luck, it's great to have a nice shed.

Neale
You can see mine in the shed thread