I actually do it backwards – this is my KISS method. Pretty foolproof and you can count on being able to import as long as you don’t add fields in the excel file. Actually, you can apply this technique for all kinds of software import/exports.
Set up your Sample Project with the fields you are going to want to import; add one activity – “Sample” – and populate the fields with sample values/formats. Then you export to Excel using Sample project & your one activity. Save the map and use it to import Excel back into Project.