You can always go back to a previous version if you want to. However, if you have the 707-300C, VC-137 or E-3 Expansion Models you will encounter errors with them.

I find that v1.3 works fine. The major difference I have noticed with it is that if I change the fuel quantity, once I return to the sim, my fuel transfer valves are closed, external power and air get turn off (if they were on) and my bleed air and aircon pack switches are turned off. Not a good thing if the engines are already running. ;)

Mark