I too find the seat less comfortable on very long journeys than the one in the 322, however the rears seem much more comfortable for the kids.

I fiddle around with the base forwards backwards and tilt during the journey so the pressure moves about a bit and I'm not sitting in the same position the whole way. Maybe save a few settings in the memory and change them about as you drive. that said I feel the seats need more squab support, even on fully up it feels pretty flat to me, but everyone is different and I'm sure that during testing the engineers thought it was probably comfortable enough..... There is nothing that can't be fixed with a hammer😜😜
FFRR 4.4 SDV8 Autobiography Santorini Black.
Fiat 500x 1.4 multiair Lounge 2015
2010 LR D4 Commercial 2.7 TDV6