If I didn't specify already, I'm also adjusting the .tga's alpha channel image in some cases. If there is blurring applied which is of a scale approaching that of the spatial frequency of the opaque/transparent parts, this can lead to more apparent artifacts as seen from nearby, and disappearance at a distance. In such case, sharpening the too-blurred sections improves things. For example, the big crane which heavily populates Pearl Harbour has required tweaking of the latticework, particularly on the upper arm. The thin crossbraces are semi-teansparent in places; this exacerbates problems. (And while I was at it, I opened up the rear two windows on the crew cabin with transparent cutouts.)
I should clarify one point. If one has a .tga for an object which has merely been repainted to a different color scheme, the alpha channels for any such variants of the same pixel array size are usually interchangeable. And so any .tga's I might supply but for which there is a preferred repaint on hand, simply copy/paste the better alpha channel to the better paint job.