Crust help

I've been after that same crust too, it's part of what keeps me baking and learning. The more I try and learn, the more I believe what you are after illustrates the difference between home and commercial baking technology & environments. Commercial bakers manage their baking environment in a much more scientific, controlled way; they must do so in order to get a consistent product. They use dough conditioners, water filtration, temp-and-humidity controlled proofing boxes, and steam-injection ovens to create a specific product day-in and day-out. They know how to make adjustments to control baking variables as needed to maintain that consistency. We can try to replicate a lot of these techniques in a home environment on home equipment, which gets us close, but often not close enough. 

That said, a few questions/suggestions for you:

1. What temp do you bake at, and for how long? 400-430F should be good enough; it appears thats what commercial bakers use to get those kinds of crusts. Lower or higher than that could be a problem. Timing is key too: the more moisture is left in the crumb after baking, the less the crust will stay crisp. Make sure you bake long enough ("long enough" depends on temp, loaf size and other factors)
2. Some crust steaming or washing is necessary. Spraying loaves with a fine mist of water before loading can help. Or egg white wash. 
3. What kinds of fats are you using in your loaves? Too much could be a factor.  
4. What loaf shapes are you using? It will be easier to get crisp crust on smaller loaves (think baguette or ficelle) or rolls than on big boules or pan breads. 

Like you, I've had some good luck with rice flour, using txfarmer's formula for po-boy sandwich breads. Still, that flaky, shattery crispness eludes me as well. 

Hi.  Don't know anything about 'shatteringly thin' but I've made some turtle crusts and I think I was baking too long and too high. Some recipe temps are as high as 450. That might help with spring but the recipes I'm baking coupled with my oven temp made me either, turn the oven down or decrease baking time.  The recipes most at risk low fat, high flour/water.  I'm also baking with a pan of ice under my baking stone which seems to be providing enough moisture for both spring and crust.  

Since my last post on the subject, I would add that I think lower protein flours will help with a thin, crispy crust. For example, I use 00 or 000 flour for my pizza crusts, and it adds a wonderful thin crunch to the final product that I just don't get with purely King Arthur AP or other higher protein flours.