Can you weigh and shake the boxes in store to get a better chance at a refractor or a redemption card? I think so, as this video proves the theory, at least partially.
I open 4 of my 10 boxes on this video, and the rest I did offline (as to not bore everyone)
Refractor Cards -
I bought 10 boxes about a month ago and weighed them all. I noticed that the ones weighing 45g on my kitchen scale instead of 44g had a 75% chance of holding a rare refractor card. I did not have that on video, so no proof :(
I bought 13 more (10 shipped, awaiting 3 more tomorrow) and from those, 3 of the 45g boxes had 2 refractors, and the other 7 boxes weighing 44g had one refractor.
Redemption Cards -
I have heard this from other Redditors saying if the box sounds loose as they shake it, they may have a redemption card. Well, this was true for me today! As you will see on the video, the inner bend of the box is almost flat, where as the ones that didn't have a redemption card were angled at a 45 degree angle "securing" the cards better from wiggling around in transport
Figuring that the other 44g boxes are duds too, I opened those after I turned the camera off and found another refractor in box 3, a prized 1A Ruby (18/25) !! Thumbnail action!!!
Thanks @GameStop for selling these!