Bustr ~
I created the sightbak folder the day when you suggested it...forgot to mention it.
I just made the color depth change on the p51bmp from 24 to 8.
Apples to apples -
In my sights folder, the default gunsight shows as 256x256 8 bit. The p51 gunsight has the same values. I deleted the original sights folder, created a new one and copy/pasted all the sightbak info over to the new sights folder...the sightbak folder still exists.
Again, the default and p51 both share the same values. And again, while I have access to the default gunsight (and a few others) in-game, the p51 doesn't appear.
Frustrating to say the least. I'm still missing a piece of the puzzle, it seems.