P3D user flightplans

Does anyone know if it is possible to specify altitude limits at waypoints in sim xml flightplans please?

I've tried creating a flightplan using Aivlasoft EFB and then saving it as a .pln file. It loads ok and shows perfect lateral accuracy but contains no altitude data. When that unamended route is shown in nav view, the sim introduces altitudes to each waypoint, many of which are inaccurate. I would like to specfy then accurately!

cheers K