Originally Posted by maxrpm
No Problem with the engine. PW150 has been derated from 8000hp to 5000hp for the Q400. Propably would need a bit more wingspan.
Close, but not quite. Derated from around 6400hp (emergency overtravel) to 4700hp (ish) for normal ops. The 400 is massively overpowered already, so you're making a quite reasonable assumption the current powerplant is adequate for a stretch.
Stretch would be interesting, but not too challenging. I barely have enough hours on type to need my socks and shoes off to add them up, but no problems handling the beastie - it seems to have attained an urban legend level of difficulty to land. It's actually quite a sweetie. Plenty of scope to ramp a stretch up to 100 seats, as even in 78 seat config, the 400 still quite roomy for the 6 footer.