I find this to be a real dilemma actually. While the JBL 12" is the absolutely central and consistent factor in jerry's guitar tone for his entire career, they just don't behave like Jerry used them when you're down at the 22 watt range like with a Deluxe. Part of what makes great tone is the speaker being pushed to or near its power limits. When they are pushed and stressed, they naturally begin to compress and subtly distort and the result is a smoothing, a removal of harshness and ice-picky-ness. I love the K120 or D120F in a Deluxe, and it really does an ok Jerry, but as soon as you drive it hard, you'll hear plenty of 6V6 distortion and thinning, but you won't get that fat, full, smooth, warmth that the JBL is capable of at higher power. Just listen to John Mayer's recent use of a JBL loaded Deluxe. When he pushed that setup, it gets really thin and small sounding, dirty and kinda wimpy. But Jerry's notes were always thick, full, rich, fat, smooth, and sparkly.
So no matter how you slice it, at lower power like that, the JBL won't quite sing to its potential. It will sound good as a perfectly clean tone, but when you try to get rockin or take a solo with a band, it won't quite deliver. Then that has one considering other speaker options, lower power speakers like the Purple Haze or Rosebud, etc. But those won't exactly nail the Jerry-JBL tone either. But they will have the advantage of subtle compression and smoothing. You can get semi close if the guitar and pickup are right and you have a Waldo buffer in the guitar and if you use the right pick and have the right technique. You can get a great sound that's in the ballpark. But generally I'm growing more and more convinced that the JBL driven too lightly just doesn't quite bring it. It takes power and loudness to make them sing, and Jerry was an absolute master of the 12" JBL's, knew how to ride them right at the edge, and even he would pop them often.
Here's an example for perspective on this. Listen to JGB Live at the Keystone 74. That is Jerry thru two JBL loaded twins stacked sideways as a vertical array of 4 speakers. If the Twin is 80 watts, then each JBL is getting 40 watts. Even at 40 watts per speaker, that super sweet tone he got there is still not as fat and full as his GD tone we know. You're hearing 6L6's distorting and those JBL's, likely D120F's, are still running pretty clean, just barely beginning to stress and smooth out. I love that Keystone tone, so sweet and juicy, but it's arguably thinner and dirtier than his classic tone many of us seek.
... and it's just like any other day that's ever been...