I don't understand these formulas. Are they so hard that reducing Elusiveness to 0 still leaves them at 10% for advanced skills? I chummed the water around the Midnight Whale and got its elusiveness to 0, yet for my 9 Zeefaring the chance is 20% and for my 8 Monstrous Anatomy it is 10%. That means base difficulty is Narrow 12 even with 0 Elusiveness. Meanwhile for my 278 Dangerous it's 83%. The advanced skills seem useless and I never use them on the Salt Steppe, though they work closer to London. I suspect it is using Zee Peril not just Elusiveness, since this is in the Salt Steppe where I am herding whales.