".pano format in full XML. The project file has evolved a lot during the engine revamp and we now have a full XML file format which is more easy to manage over version release. So you won’t be able to reopen 3.5 .pano file with older version. If you need to do that, we added a ‘save as old .pano’ export so you can convert this .pano XML format to an old one. Of course, some aspects cannot be transfered like many parts in the optimizer settings which are totally new."