Very nice!
The last time I tried to do a natural light photoshoot, a gust of wind lifted the posterboard and flung my La-5 to the patio. Amazingly, one of the gear struts snapped, but there was no other damage. But from now on I shoot in the garage.
But yes...love the way the translucent plastic knocks the worst of the harshness away.
A few other things you may want to try, for kicks...
First - get into manual mode and set the aperture as low (largest f/number) as you can. This'll help keep ensure all of the model is in sharp focus. Not that I see any focus issues, but I know I suffered from them pretty bad when I first started trying to take decent pics.
Second - you may want to put the tub up on something so you can get down for some lower-angle shots. I find they give the most "presence", especially on 1/32 kits. Well...except for Spitfires. For some reason they just look funny from a low front angle.
Third - if you have Photoshop, try out the Unsharp Mask filter! This is armor, but it gives a really good idea of the effect it can have:
Fourth - I'm still experimenting with dropping a kit into a real-life environment (need to work on my diorama skills instead of just using a grass mat!), but I've found it helps to "beat up" the kit image a bit so it more closely matches and blends into its surrounds. This one got some nice, harsh contrast, some serious magenta thrown into the overall color balance (since that's the way so much WWII color film seems to look), along with dust and grain. The background and sky are both photoshopped in: