Thanks NiLuJe! JimmyR also helped on another thread
here - this forum is remarkably active, I really love it!
I installed update_KUALBooklet_hotfix_v2.7.22_install.bin, then JailBreak-1.16.N-FW-5.x-hotfix. KUAL is now working, MRInstaller too - my only issue is that the books are all missing. They're on the device in /documents but not displaying in "Your library" - if you have any ideas, let me know!