1) GM does not publish chassis stretching guidelines. That means RV makers or modifiers assume the risk of their work and design. MOR-RYDE simply uses the Ford guidelines on the Chevy chassis, but they still assume additional risk doing this.
2) GM has had two extended supply delays of the 4500 chassis. Production was stopped without notice, and the stoppage continued longer than expected.
3) The E450 has a higher FAWR, allowing longer wheelbases for the longest coaches.
4) GM has a small service network for the 4500 Express