Wit my Flash 62:
* sleeping bag, cloths, sleeping pad, food and stove in the main pocket
* 1st aid and 'cat hole' stuff sacks in the brain
* water filter (and anything else that needs ability to dry out) in the side mesh
* camp saw, other toiletries, misc gear in main pocket on back of pack
* tent (poles, stakes, ground sheet) in tent bag in bottom straps.
I must say the buckle took some getting used to for cinching the straps down tight. I've found the straps to be sort of slick in terms of side to side movement. The straps have never loosened, but if the tent isn't cinched down tight, it tends to slide out the side of the straps.
I once encountered some branches blocking the trail. I decided to take a few minutes to cut them out of the way. Since it wouldn't take long, I didn't bother to take off my pack. But the sawing motion was enough to have my tent slip out of the straps and slide about 25' down a steep embankment.
Normally, to prevent such an event from happening, I usually pass the buckle thru the cinch cord loop of the tent bag. That way, if the tent bag slips out the side of the straps, the straps at least hold onto the cinch loop to prevent me from loosing the tent.
On that particular day, I had not passed the buckle of the straps thru the cinch cord loop.
I've since learned to cinch the REI Flash straps tighter, and pretty much never forget to pass the buckle thru the tent bag cinch cord.
For a 2016 JMT thru hike, I purchased an Osprey Volt. It too has straps at the bottom that I used to lash the tent to the outside of the pack. But those straps are wider and easier to cinch. Didn't have any issues with the tent slipping in those straps.