Is there a trick to it? The Polypropylene on Polypropylene is slick and unless I'm missing something only similar cases, ie 1510 on 1510's, 1610's on 1610's etc are keyed so they'll stack. I've always wondered if there was a better way, I currently throw my foam core bounces between one level so it grips a bit better, but is not ideal. I've thought about trying some grip tape but have yet to get around to it.
I stack my Pelican cases all the time. While you're right that stacking the same cases on top of each other is the best fit, stacking different sizes shouldn't be too much of an issue. I imagine the weight of the case with the contents, along with gravity, is enough to keep everything secure. That is, unless you're stacking it super high, then I would imagine you would lose playing that Jenga game lol
I stack several pelican cases all the time in my closet. Larger on bottom to smallest on top. If your traveling with them use a cargo strap to bind them together.
