I have very flat feet, and am an over pronator. For most regular shoes, I use Blue superfeets, and finally ended up getting custom orthotics made for my cycling shoes. The Shred soles, while much better than most stock sock liners, didn't have enough structure under the arch and didn't work well for me. Super feets have hard plastic to maintain the shape of their arch, and my custom orthotics are molded plastic. SOLE's also have harder, less flexible material in the arch but it wasn't high enough for me.
A quick test you can do is to wet your feet and then walk on a cement floor. Look back at the wet imprint your feet have left.
If your imprint looks like the far right, than I'd suggest not going with shredsoles.
Great guy, neat company though.