Scout, Gazelle (normal and armoured) and Bell 212 were without doubt the worst seats I encountered.
I recall an American pilot (an old friend of ours with a Hungarian name Sasless) telling me about a known condition suffered during and after Vietnam called "Bell Back" which was a result of extended operations in the slightly nose down attitude adopted by Bell pilots as a result of fatigue. The only way to ameliorate it was to wear a back brace similar to those worn by weightifters or riggers.
NEO