Paper is astringency. Usually brought on by lack of pH control. 90% time it is lack of sparge acidification unless using RO water. I dig the SO4 "bite and thickness" and IIRC Martin described it as "crunk". My IPA's get 300ppm and Terry Foster advocates much higher than that in his ale recipes (650)... That said, mash and sparge pH is 5.4. Water treatment is 2 phases. Proper pH FIRST, then "season to taste". Alot of guys get it backwards because gypsum can reduce pH (but usually not enough and then acid must be used). If you have pH dialed in and still have some astringency, you need to look into polyphenol reduction (polyclar) or good old fashioned longer lagering for it to drop naturally. As a BJCP I am gonna ding you if crunk is missing (save and except for NEIPA)