Hi Olddog,
some of the older add-ons included other files sometimes.
Some could have been flight files, (.flt) dat files, etc.
So some things might get mixed up that aren't supposed to.
When you are modding your 1.28e, what are you doing? And what are
you using to switch files out? OAW? Or what? Let us know.
Some add-on skins and planes came with a .flt file which was good for
1.2 or 1.26 but will not work with 1.28e. But 1.28e might have a .flt
file that will work for that plane. Let us know what you are trying to do
and we can probably get it working for you.
But before you do alot of experimenting with old mods, you really should try
the 1.28e available stuff first. Vanilla 1.28e is excellent alone, but you
should try ETO_01!
ETO_01 goes with the new 'Planes' and 'Sounds' folders.
When you load your ETO_01 dirset file and start the game and go to configure,
you will get this:

This screen will allow you to select 1 of 4 planesets, or plain 1.28e.
The 4 main screens:

Some of the plane selction screens:

Some of the hanger screens for selected planes:


There is also a seasons folder in ETO_01 that changes your terrain with
the season.
After you have played around with this for awhile, then you might want to download
some of the scenarios that were modified for 1.28e. (SPAW, SAW, DAW, FAW, BOB, SWOTL.)
Any problems or questions, just ask here!
AO