Hi Grog,
I have a pair of Specialized BG Comp Motodiva shoes. They're probably very similar to the shoes you currently have, but the Motodiva's don't have a carbon sole.
I haven't noticed any issues with the sole not being stiff enough during riding; my longest ride in these shoes has been a 60 miler, but I have 70 miler planned for Saturday. I feel pretty comfy walking in these shoes. My Shimano SH-M036W shoes are more comfy to walk in, but I don't think they're as stiff as the Motodivas.
Hope this helps.
-- Melissa
I'll get back on the bike soon, I promise!