Original sentence: Baseed on experience with the earlier SZD-6x Nietoperz  and SZD-13 Wampir tail-less gliders the 'SZD-20x' was an all wood flying wing, with the pilot sat in a pod extending aft of the trailing edge on the centreline, and large swept fins & rudders at approx 2/3rds span on each wing
Edited sentence: Baseed on experience with the earlier SZD-6x Nietoperz  and SZD-13 Wampir tail-less gliders the 'SZD-20x' was an all wood flying wing, with the pilot sitting in a pod extending aft of the trailing edge on the centreline, and large swept fins & rudders at approx 2/3rds span on each wing