I used to work for a company that dealt with amongst other things rawhide drum heads. We would get them from overseas by the thousands. Unfortunately there was a screw up once when they left the hides in the caustic too long and they just could not take the strain after that. We of course had no idea just how long they let those bad drum heads soak, it could have been extra hours, days, or weeks. I recommend (not having done it before) that you check the hides often and pull them as soon as you can, even if it means a little more elbow grease in removing the hair. You could also wet your hide and then use a commercial hair removal product such a Nair(or generic). That is what we did when reheading African style drums that need to have the fringe of the head with hair on it. Shave the hair with clippers while dry, then treat and use the top of a soda can or old credit card to scrape the hair/stubble off. With your experience, you should do find with the caustic soak though.
Swamp