Graoumf, who's translating the latest version into french, pointed this out to me, and I'd like to hear what other people think.
The description of the Ripper specifically says it requires 18 strength, but I didn't notice that at first and just glossed over it and set it to 15 str and 11 dex like all other composite long bows. My inclination is to set it back to 18, since if the developers wrote that in the description, they obviously intended for it to be used only by monstrously strong characters.