A Saito 72 is a 4stroke with a tube for an intake manifold from the carb to the head, right?

Mounting them inverted can give problems.
That pipe from the carb to the head is no problem when those engines are mounted 90degrees or upright. Any raw fuel drips out of the venturi when the engine isn't upside down. When it's upside down, every bit of the stuff is caught. So you really need to work out a fueling proceedure that doesn't allow siphoning to start, and a priming proceedure that is on the safe side.

4strokes already have a pronounced tendency to backfire. Make sure you don't increase that. And they'll hydraulic lock easier upside down too.

Turn a 2stroke upside down and siphoning or excess fuel drips out of the carb onto the ground. Turn a 4stroke upside down and those intake tubes can hold up to a couple of ounces, and will hold everything that would have dripped onto the ground. Everything.

An awful lot of hard to start engines are that way, not because of the engine but from how the modeler worked with the airplane from the moment he started the fueling process.