OK - since I first posted I have been experimenting with doing alternate long rides in my old shoes, and the newish Tahoe's, and I am definitely getting a lot more pain with the Tahoe's. However I am a bit confused about the advice here about the Specialized inserts
This is probably a stupid question but I assume you mean replacing the original innersoles with the Specialized footbeds, rather than putting the new the footbeds on top of the original innersoles.
My bigger question is whether the separate footbeds you can buy actually provide that much extra support compared to the standard "Body geometry" innersoles that come with the shoe. The main difference, apart from the extra arch support, seems to be the "metatarsal button".
I can see that the "metatarsal button" offers a bit of extra support and stiffness but it doesn't look that substantial to me. Even the guy in the Edinburgh Bike Co-op shop who I spoke to about certainly wasn't convinced that it would make a major difference - he suggested investing in a good pair of cushioned innersoles designed for running shoes instead.
I would also be interested to know why
@Dragonwight thinks that the matatarsal button "is a real pain".
Anyway, in summary, I am more than happy to fork out for some footbeds if they are likely to make a difference but would first be interested in knowing what other people's experience is of using them.