I have been using the DLBP in an island
2 degrees bellow the ecuador, so hot & humid is the rule around here, except when is hotter & sticky damp.
That reference given, there is a DLBP feature that is very nice for our kind of climate and that at first I gave no importance, and sets it higher then the PCBP, the removable
waist belt.
When I received the DLBP, I thought it to be useless... hey... who needs a waist bag in such a lightweight backpack thought the naive novice TB bagger.
But decided to not remove it... as I t tried various straps lengths, the belt went from waist to chest belt but during the experiments, I found that whatever position you may find comfortable, the waist strap is fantastic to use in a hands free one shoulder single strap configuration, because it keeps the DLBP secure and slightly to the side, reducing the contact area and allowing the back to breath better.
In the weather here, specially running urban errands, that makes ALL the difference!
HTH