Perhaps this has been addressed before, but is it simply just of question of board (side of contact) pH, or rather the capacity of the board to interact with the comics and alter pH, or buffer changes in comic paper pH that might occur naturally? Is the goal simply to have support that won't generate an acid insult? I'm sure you don't want a highly basic board, as I assume paper has some preferred pH range. It seems to me you want a board that maintains a non-damaging pH over time when stored with a comic, and ideally it has some buffering capacity to mitigate enviromentally- (or book-) induced changes in pH.