I agree that Portsmouth-Cardiff services need 4 carriages, but FGW just don't have the stock at the moment. 150s are better suited to short distance services, and the use of 158s on Devon local services and the Falmouth branchline was clearly excessive. 158s would be much more suitable for Plymouth-Penzance and Bristol-Weymouth services though. The influx of Class 150/1s with 2+3 seating has made journeys worse on these routes, at least the Class 150/2s had a decent interior.