Insulation is far more important than location. Use heavy duty PVC insulation tape to insulate the inverter from any stray wires or PSU connectors, as well as the case and mobo itself (I usually use contractor-grade tape). FYI, inverters can fry the chips on your components fairly easily due to the fact that they are AC-based, so insulate the inverter(s) properly to ensure that nothing gets fried accidentally.
With proper insulation, you do not need to be bothered about where you place the inverter.