Big P - I come from a background in 20mm too (back when it was was just Airfix, Fujimi and Matchbox). I still feel that attraction of that scale, which is one reason I like seeing what you do with it. But having tried 15mm (too fiddly), I've moved towards 28mm, and am finding it a good scale to work with - in part because my declining eyesight, but also because it's a wargaming scale, so I'm not always comparing what I do to stuff built out of etched metal and brass...
As I commented on your Dakka thread, I actually think your style is better suited to 28mm, because your chipping/rusting/streaking effects are (IMO) more 'in scale', whereas on the smaller scale it can look a bit overdone (the Churchill and Lloyd Carrier in your photo look very nice, but the Panzer III looks like an antique).
I've build the Rubicon Panther as well, but it's the Ausf D and not the Ausf G. The Ausf D has some accuracy issues, but the basic kits goes together well. I'd really like to see you tackle a couple more models in this scale.