I know this thread is old, but I just got some stunning results from Strathmore Bristol paper the Formulary traditional cyanotype chemistry, double coated. This is a very smooth surfaced paper that produces great details and tonal range and holds up well to washing without getting rough afterwards. I have no idea what the pH is for certain, but I found one reference to it being around 6.x. I can send you an example print that I did the other day (4x5) and a few sheets if you want to try it out.

- Randy