And, Terry,
There's also a thing called choking the engine to draw fuel for starting...
Some engines have short front ends, and very short stock venturiis. When mounted inverted in a full-body model, adding a longer extension makes choking a bit more possible... I've used exhaust header (hi-temp neoprene?) tubing to hold such an extension onto a Fox 35 on at least one such model. About 3/4" length of 1/2" OD aluminum tube; fit the neoprene tube over the bell at the top of the venturii, and lashed it on with fine copper wire.