With rear intake engines an air filter will absorb the dripping excess fuel when starting. And catch the flash back spray. I make filter holders sometimes from pieces of plastic and also buy the trumpets from A.I. and zip tie filter foam around the intake. For filter foam I buy an airfilter for 70's ford 390 pickup engines at Napa. They come with a nice piece of fuel safe foam to cut to size. Makes about 10 filters.
After 4 years doing this with ZDZ BME and 3W rear carb engines I have yet to see one drop of fuel leak into the engine box of any plane.
http://www.aircraftinternational.com/...<Trumpets