Moderator note: Just to let you know that we don't allow links to surveymonkey on this site. They have resulted in users being spammed in the past. The software on this site will allow you to set up a poll here. I have also deleted your duplicate posts, another no-no.
If a backpack causes pain, it hasn't been fitted properly. Look at the
home page of this site, left hand column for articles on how to select a backpack that fits.
Backpack fit is almost as individual as shoe fit. The pack needs to fit the specific user, fit the specific gear (s)he is carrying and be comfortable for the user with the gear packed inside. The user needs to acquire his/her other gear before shopping for a backpack and then box up and take the gear (plus the equivalent in weight and bulk of several days' food, plus a day's water) along to the store.