There is no reason to dive stages at the intro level. Want to go modestly further on your 1/6ths? Go up a size in backgas from the 85s to 95s or 108s. Even if you did have an AL80 to use as a stage bottle, bringing along stuff you haven't been trained to actually use (especially in a cave) is either going to damage the cave or get yourself killed (which gets caves closed and/or damages them trying to get your body out)
This is a huge no.
This is a huge no.