Should be fine IF----
You need to do all work on the doors with the cabin lid at least clecoed to the fuse tub. If there is any twist or misalignment of the top, your doors will be fitted to the same twist etc.
When you bond the inner and outer door parts together, you pretty much lock the door shape in and it is not going to be easy to change it.
Rough fit things, fine. After the cover is riveted on, final fit, and then bond the door parts to each other.