Complex sentence: Although considered a very advanced design, the operational suitability of the wing nacelle turret installations was questionable: P.108s and B-17s had three turrets as main defensive armament, but the latter also had ventral, dorsal and tail gun positions.
Split into simpler sentences: Although considered a very advanced design, the operational suitability of the wing nacelle turret installations was questionable. P-108s and B-17s had three turrets as main defensive armament, but the latter also had ventral, dorsal and tail gun positions.