I agree with Skyking's principle that the Skymaster is a fundamentally far safer aircraft than a single or a conventional twin. Regretably, however, you're right: the statistics don't reflect it.
But a more careful analysis shows that in most instances it's not the aircraft.
One of the top threads in this message board is entitled "Skymaster Info" and one of the links there is
http://www.skymaster.org.uk/purchase.asp
This is a compilation of info from Skymaster owners and experts over the years about things you should know before you buy a Skymaster. I suggest you read it carefully. The following is excerpted from there:
"If you look at the accident statistics of Skymasters, its record is comparable to other twins with retractable gear. You'd expect better, when you consider that the plane was designed to be very forgiving and easy to fly compared to a conventional twin (without the tendency to yaw over when you suffer a failed engine at takeoff). But it's precisely because of its apparent simplicity, some contend, that problems arise. Too many pilots think they can get in and fly, and you find, for example, an unusually large number of accidents due to simple fuel starvation because the pilot didn't check fuel or because he/she didn't know how the four tanks feed the engines. You see, because of its reputation as a bullet-proof aircraft, some pilots treat the 337 as if it was a simple single-engine aircraft. But it isn't. You don't just get in and fly. If you treat it for what it is - a complex, high-performance, retractable-gear, variable-speed-prop twin - and if you maintain it properly, and if you do thorough pre-flights, and if you stay proficient, then it is indeed a very safe aircraft."
I have now a 337G and used to own a 337D. To the above, I would add the following. Like most twins, the 337 has an anemic climb rate on one engine. So an engine failure on takeoff (no more likely than on any other twin) may be far easier than on a conventional twin and far safer than on a single-engine aircraft, but it's still an emergency. If you're overloaded, if your remaining engine is not performing up to par (perhaps because you've been delaying putting in a new set of plugs), or if you don't promptly implement the necessary recovery procedures (best single-engine speed, full throttle, full RPM, identify and feather bad engine, reduce drag, etc, etc.) you're in a heap of trouble.
So we're back to the last sentence of the earlier paragraph (in quotes): do it right and it's far safer.
Ernie