Very good build and I like the weathering.
Re:track sag, try using either the pin technique or the thread technique to make force them to sag.
Re:weathering, my other comment is that perhaps some of the decals be chipped off as well, since it appears that some are over the chipped paint.
Overall, a very good build indeed and very realistic!
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BTW, I noticed you stapled the tracks together. Try using either thread and sew it (I did that to my Strv103B tracks) or better yet use chloroform. I used chloroform to solve Dragon's vynil tires problem (the tires split in time, using chloroform welds them back together as if one whole piece). Don't get carried away with the chloroform though, it's quite strong stuff.