Select pictures, right click on picture and pick Export Selected Photos ( or go to File/ Export Selected Photos), on the Export Photos Menu pick your location and sub folder, pick "Use unique names without warning", and most important pick Naming Format "File Name". If you selected all your Project pictures by selecting Pictures All, then Ctrl A, you will get a copy of all your photos that include the original name, tags you assigned, and faces you picked that are "People" in the jpeg file details.

Here is the best part, Start a new project, and import the file ( subfolder where your new pictures are located). The new project contains all the pictures with the tags. Then comes the best part. Select all pictures, then click on "Tag Faces". The program will run and then come back with a message that no faces were found. But check out the Faces list and you will find that all your face data is restored to your Project.

I did this with 8,430 pictures, the only problem is that I had not selected "File Name" so I lost all my original picture names. Further test on smaller projects with "File Name" proved successful.

This is how you can combine projects and keep all tags and face data. I wish I had known about this last week before my large projects were corrupted. I would have saved pictures in groups of 500 - 1000 then I could reassemble my main project. This might be a good use of Albums. One down side is that you do lose your original Folder, but I include the folder as a tag on Import.