First lets address some of the obvious shortcomings of multiple engine design. I would think the first problem to multi-engine design is not with design at all, it is the pilot. The pilot must be properly trained and/or educated for multi-engine aircraft. Complexity is a second issue of multi-engine design and is much of the reason for the first problem. Complexity can by modern design be reduced from the contemporary norm. Others thoughts and ideas on this matter is one of the main reasons I am posting this argument. Efficiency is a third issue of multi-engine design more engines and the related components create more drag. So why multi-engines? Well lose an engine over an expanse of water, mountainous or otherwise hazardous terrain and you may wish you had at least one more and maybe two or three additional. So despite the additional workload on the pilot due to the complexity of the machine it can become safer to have an additional engine or engines under certain conditions. Also it can be more efficient in regards to operation, if you have three or more engines and have a engine failure your options are greatly increased as to were you terminate your trip. You may wish to choose an airport more cost friendly in regards to getting repairs for instance, or perhaps you would prefer someplace with a longer runway and or better weather. My personal belief/opinion is that one of the biggest problems of most small multi-engine airplanes is that they only have two engines and that small light multi engine aircraft with three or more engines would be safer than two engine aircraft. One of the drawbacks of a two engine design is that after considering drag you end up with something less than 50% power with an engine loss and with a large number of designs this is inadequate. With three engines you would end up with something around and possibly more than 60% power with an engine loss and also less losses to drag because the yaw will be less pronounced even on the critical engine (three engines 33 1/3% power each, two engines 50% power each, 50% minus 33 1/3% equals 16 2/3%, so a reduction of 16 2/3% of the power effecting yaw). Because of the reduced yaw a three engine airplane is easier to control and is more efficient with an engine out. Also it may be possible for a three engine design to be lighter and have less drag than a two engine design because the nacelle's and propellers would be lighter and smaller and part of the middle engines drag component could be married with the fuselage. Three engines in the 50hp to 60hp range would make a nice two or three seat cruising airplane, and three 80hp to 100hp engines would make a nice four or five seat cruising airplane. Considering the cost and maintenance expense of 150hp to 180hp engines or of 240hp to 300hp engines the actual cost and maintenance of a nice three engine design may defy conventional thinking. I am looking forward to your thoughts and comments on the subject, thank you.