In all honesty anything above 470 accuracy for turn 5 is fine, you'll still have a 99.8%+ accuracy rating. However gryphonskin offers 1-2% parry at most, the next tier of block/parry strength and a little more damage/enmity generation in exchange for 363~hp(well a little more than that when you factor in shield oath/defiance). 5 Melded gryphonskin is fine however for current content as it'll leave you at around ~6600+hp which is perfectly fine for turn 5. HP just allows for mistakes and reduces your chance of getting oneshot by twintania. Overall you're increasing your RNG based mitigation in exchange for solid visible health.