Have to admit i also have drams gripping the bar, but only when doeing 100kg deads, i usually get out 5 before I feel my grip will fail, usually teh last two All I have holding it is a few fingers as my grip has come undone,vie thumb is not touching the bar, I use a front back grip. chalk does help heaps esp, if it is just a slippery issue.
At 80 kg it is too easy to hang on for a set of 10 go figure..that 20 kg makes a huge difference.
but since doing deads i have noticed a reall gain in my lats, delts, gluts and traps., but still not quite at 70kg....yet