Honestly, for short track I want the linear but divey feel that the soft bushings in the front with less bushing volume in the rear provided, just with a bit stiffer center. In my experience more bushing volume means that for a given stiffness in the center, you have more support while leaning in deep. For short track, it’s the opposite of what I want.
Therefore, going lower in bushing volume, but up in bushing duro, should feel like the jump from APS to WFB did. I should be able to go up in center stiffness, without going up in stiffness at high lean angles. Or go down in stiffness at high lean angles, and keep current center stiffness.
Your suggestion meanwhile seems like a more long track focused setup. You need much more support from the bushings while cornering on long track vs short track. I want this setup to work well for like medium sized tracks and short tracks - I don’t need to be able to take corners at 40mph.
I think what made the previously well working bushing setup feel too stiff was at least partly the super low temperatures - we were racing close to freezing temperature, versus having the setup tuned in at around 20C celsius / 70F. I haven’t measured the durometer of the bushings, but the tires measured like 13A higher compared to 20C. I think I might have just tried 100A WFB on accident 
After I switched back from the loose setup to the double chubby setup for kartplanet, I noticed that the trucks are stiffening up on the edges the more I lean and the contrast from chubby / barrel was quite large.
Honestly the chubby chubby rear setup felt kinda like @TZDKB 's new setup on chubby / barrel in the rear, but there I think the reason for the progressiveness was from the ride height and lateral G pushback, vs on my board it came from bushing volume.