I've never tried the Buxton... I think that is the paper that Dr. Ware refers to as the least 'hostile'.

I think that one thing that may be of assistance to those that wish to have precise control of paper RH is the use of a Sword Hygrometer, it is used in paper manufacture in testing the RH of the rolls. With a small stack of paper you could just insert the blade between the sheets and get a very precise reading of the actual RH of the paper.

For myself I think I can solve the humidity problem by sunprinting on rainy days..... cheers