not so happy with the answer (which i expected that way, almost word by word)
to clarify:
if i open an .obj (im not "importing" it) the working process remains in .obj format.
changing it into an .ac and export it then into .obj again is not only weird, it loses the attributes anyway. AC3D seems not able to hold other than 1 texture information.
It will lose the .LIT, the .NML, the specular, the blend, the RGB, everything.
Opening the saved.obj file with a text editor is best way to verify.
Anyway, whether you open or import content, the file name to show in the title bar is not a thing you wanna miss when working on complex aircraft. I can not think of any valid excuse.
as mentioned earlier, i am not going to purchase another "upgrade" of AC3D for 3 reasons:
1. These are basic issues that should not urge the customer to spend money.
2. from my experience, i don't expect improvements. AC3D has not come with substantial value being added to new versions. I don't think anyone is even developing this tool any further, it doesn't feel like.
So, no considerable changes between versions.
3. Laminar's Ben Supnik said the x-plane plug-in is no longer supported nor will it be updated. That was more than 2 years ago. So i don't think there is a change to that with any version later than the one i already have.
still using AC3D, but my happiness degree never exceeded 60%
If just these and some other downsides weren't there!