delta drag
It's important not to increase the wing loading. Therefore you can only make it smaller if you also make it lighter. It will be difficult to make it lighter if you are adding a streamline cowl for the engine and pipe. If you want to go much faster you must do every thing at once. NOTHING can hang out in the breeze. EVERYTHING must be inside. Space for fuel tanks can be solved by using bladder tanks. To save weight, don't carry any more fuel than necessary to take off, do a two way speed run and land immediately. If you are to succeed you must become fanatical about every possible drag and weight reducing measure. Nothing can be compromized that interferes with these goals. To beat the Diamond Dust by 22% you will end up with a plane that has just that one limited capability and nothing else.