I got Wizard with both Heistotron and Hospice Morty. I got my only Miles Knightly with a Heistotron, and my only Asher Hiss (the snake) with my only Death Tree Morty. The snake and death crystal Morty were from a Case F (the guy brought it from the back and opened it in front of me), so I'm guessing Wasp Rick is in Case C, at least at GameStop.
The chases were not always top middle. I know for sure they were bottom middle once, and some other cases might have been messed with before I got to them. In general, I would say test the middle pairs. If they are different weights, buy them. If they seem the same weight, I would say the heavier pair is probably the chases (compared to a pair of space suit Mortys). In the case of the snake/death tree Morty pair, however, they were similarly weighted and not very heavy. Needless to say, most of the common dupes I ended up with were Space Suit Morty, but I also got a few extra Teddy Ricks, from cases that I assume were either mixed up before I got to them, or maybe if they were in the back bottom in some layouts.
I assume Wasp Rick has to weigh a lot and takes up the most space within the box, maybe that will help.