I sometimes use my DX7 with RealFlight G4.5. It hooks using the cable provided with RealFlight - between the two controllers (DX7 Interlink Computer). It's ok, but I do see much benefit (other than add wear and tear to my DX7 and to get familiar to the DX7). You don't have all the channels (e.g. the CH5 rotating dial on the Interlink is not available on the DX7). There is some limit to the channel mapping, and you don't have the reset and select buttons for RealFlight (you have to use the keyboard).

Gilles