The main problem with inverted engines is proper location of fuel tank in respect to spray bar of throttle. When inverting an engine often the fuel tank will be too high, thereby causing fuel siphoning. Get the tank in proper relation to spray bar and get engine tuned and it run fine. If it runs too rich, due to siphoning or improper tuning it may kill glow plug. other than those 2 things engine doesn't know it's inverted and will run fine. At times it may be necassary to use a glow plug lighter.