First use of the new rack/bag/pannier system today. I went for an adult beverage run. I bought a 15 can pack of beer, and a 26er of both Luksusowa vodka, and Crown Royal.
Two rookie mistakes were made:
1) If you're going to buy two glass bottles of anything, bring something to separate them. Clinking and clanking over bumps is obnoxious.
2) On the way home I started hearing noises... tick tick tickety tick... I stopped and found that the ends of the elastic cords that fasten to the bottom of the pannier racks were lightly hitting the spokes on both sides of the wheel. Sorted.
As you can see, a 15 pack just barely makes it into the pannier. It's stable and in no way in danger of coming out, but you can't close the top.
A little lopsided.
The rack has a suggested weight limit of 20lbs as I recall, and this load would probably be around 15 - 17lbs I'm guessing.
Riding was easy. No noticeable issues at all with the exception that you need to be prepared for the extra weight when leaning the bike over.
The rack stayed put with zero issues. No shifting or moving over about 9km round trip with obviously half of that loaded down.
Tomorrow will be a grocery run. I will add the backpack to that experiment.