I have a funny story to tell. Today I brought my SIDIs to a store that sells SuperFeet insoles. The store associate chose the Black version designed for people with flat feet. Although it put slightly less pressure on my arches, it really made the entire shoe feel tighter since the insoles filled up more volume.
I'm walking around the store and the guy says "Hey, did you ever ride in those new shoes yet?" I said, "Not yet, since I wanted to be able to return them if there wasn't anything that could make them more comfortable" The store associates laughs and says "Get out of my store, get on your bike and ride for an hour. If it bothers you afterwards,THEN come and see me!"
I'm glad to hear others experiencing the same arch pressure issues initially, but hope that it goes away like you mention. We'll soon see.