Hmm.....I think I'm getting closer to pulling the trigger on some shell Park Aves. Sadly, I doubt that anyone stocks multiple models to try!
Conensus seems to be to go down in length, and in most times up in width. However, the shell models may fit looser than calf. I doubt it's a size width's bigger though, so I think I'll go 8.5E (TTS 9D)
I suggest trying on a calf version and going with that size. We have approximately the same size foot, so I agree you will likely end up with 8.5 D/E.