I have a 1975 P337G skymaster. The Cessna POH states single engine operation is 18,500 feet either engine. Before the P337G, I hand a normal asp. 1972 337F skymaster. Don't remember the exact numbers but they are something in the range of 7200 feet for rear engine and 5000 feet for front engine in single engine condition. I did lose the front engine once on the 1972 plane when I was at 10,000 feet. I was able to stay at 8200 feet with rear engine.
Jerry
N34EC
