Boot board to stiffen approach shoes?

Climbing down here in Patagonia for the season and trying work out the kinks in some lightweight shoe/crampon systems. We climbed De’L’S yesterday, using approach shoes and Petzl Leopard strap on crampons for the glacier travel and the 50* snow slope to get up to the rock. While it did work, kicking steps in the firmer sections of the steep snow (obviously) proved less ideal. Has anyone found a way to put a stiff material or boot board in the approach shoes to take out some of the flex for climbing moderate snow? Any and all ideas welcome!

ECD H wrote: may work better to tinker with stiffening the crampon instead.

I'm not sure that would work, as a flexible sole and a stiff crampon may spell trouble - hiking crampons are made specifically to be able to flex with the shoe. I don't know if a hiking crampon would work for the OP, as 50 degrees is kind of pushing it, but maybe look at something like the Kahtoola hiking crampon or Camp XLC 490. I've done plenty in just a 10 point 3/4" kahtoola hiking crampon, but kicking steps in hard snow isn't that fun in 'em. 

My wife needed something to help immobilize her foot so that it could heal from an injury. A foot doctor simply cut out carbon fiber inserts. Super thin so you could barely notice it was there from a sizing perspective, but reduced shoe flex to near zero. Wondering if it could work for this application as well. 

Following Steve G, I have seen online, at places that sell orthotics, carbon fiber inserts for, say, hallus rigidis, for example. Like this: https://www.myfootshop.com/spring-plate-carbongraphite-fiber-insert.

don't know if that would work or not, but this may be the kind of thing to try

Steve G wrote: My wife needed something to help immobilize her foot so that it could heal from an injury. A foot doctor simply cut out carbon fiber inserts. Super thin so you could barely notice it was there from a sizing perspective, but reduced shoe flex to near zero. Wondering if it could work for this application as well. 

Ahhhh yes this is the type of thing I was wondering about. Just somehow have to get my hand on a pair and try it out. 

Years ago I was recommended by a climbing shop worker to use a piece of thin plywood (outdoor grade presumably) so I could make better use of my hinged crampons...my boots were only slightly stiffened with an extra layer of thick leather between Vibram and boot. I never tried this method myself, presumably it would be more comfortable with the wood under the insole (or a cheapo thin one).
     Incidentally probably the most versatile climbing footwear I've ever had were Messner boots with a suede upper and high rand all round. They were actually stiffened with plywood beneath the insole, took crampons fine for step kicking in neve and easy ice, and were great for walking and rock climbing as well as being really light. I needed to wear plastic bags over my socks if conditions were wet. Sadly they had a limited life due to the plywood cracking up in about the 4th week of heavy use.

Those orthotics carbon insects work quite well.  I use them in trailrunners with crampons.  A stiffer approach shoe they would probably stiffen to almost the level of a mountain boot.
The biggest advantage I see with them is that they allow to have a very soft shoe to run the approach/descent. ​If it is hiking in snow to get to the climb I would probably just take a stiffer shoe/boot like a Ribelle Tech.​​​

The Hybrid crampons with cord are a lot less stiff than regular crampons with soft shoes but as mentioned at least they won't break.