...Just discovered also that it was also necessary to remove any FTX region flatten elevation fixes from Scenery/World/Scenery folder as when I just unticked the regions in my scenery library many elevation problems arose...I just backed them up from from Scen/World/Scenery and and then removed them at the same time I unticked the regions in the sim...worked perfect...to reinstall regions i just re-ticked the sceneries in the sim and repasted the backed up elevation fixes into Scen/World/Scen...hope this helps someone...I'm no expert but wanted to share this discovery...cheers ..Pete