Lets see, if the Olympus weighs over 6 lbs. complete and the P120s weigh say 3.6 lbs complete, then 2 P120s adds up to 7.2 lbs. So you pick up an extra 1.2 lbs from the engines, another 1 lb from the extra fuel tank and tubing. Don't forget addition bulkhead and support for the other engine, say another pound. You'll probably carry an entra 2 lbs of fuel, I think 40 oz., for a total of 240 oz of fuel. Thats 120 oz of fuel per engine, good for any 8 minute flight with reserve. So if you add it all up, you have an extra 5.2 lbs at take off and landings around 3.2 lbs more then Buck's F18 which weighs in at 32.5 lbs. I think some of the F18s out there probably weigh in around 35 or 36 lbs and still fly well. All that considered you have the safety of two engines instead of one and your added cost is that of the engine, fuel tank (a 40 oz Dubro for $15.00), and an extra pipe (according Shaun the two single pipe would be cheaper then the split). I think it's just a cost and time issue. Do you spend the extra time and money to make it a twin and have plane that will make it home should you lose an engine. I have had planes come home safely after a flame out and I have had planes that did not make back so gracefully after the engine quit.

Sung