Hi guys, even though I don't run the K&N setup any longer (it's now on Sonic's car), I've put some thought into this problem and suggest the following.
When installing my filter, I realized that the plastic MAF housing was going to be an issue. It is smooth plastic, and pretty soft, so if you do overtighten the filter clamp, it's going to break, no doubt. Mine didn't crack like the pic above, but it did fold over itself and crush slightly until I realized that I had overtightened it.
Instead of tightening the clamp until you crush the housing, which will ultimately leave the filter loose and allow it to fall off, what we need here is more friction between the filter shell and the MAF housing itself, without having to overtighten the clamp. My thoughts were to get some of that industrial velcro and with a little Super Glue to help hold it, wrap a strip of the hook side around the MAF housing, or the inside of the mouth of the filter. This will create a nice amount of friction between the two pieces that would allow you to run the clamp down snugly, but not overtighten it. If that didn't work, I was considering using a strip of 200 grit sandpaper instead. Same concept, just glue it to the inside of the mouth of the filter, or around the edge of the MAF housing to increase friction.
Just a couple of ideas to help those that may be experiencing the problem.
2014 ST3 - Tuxedo Black with Full Leather Recaros, Sunroof, Nav-Sync-MFT
My other rides -2006 Performance White Mustang GT Coupe, 2004 40th Anniversary Edition Mustang Coupe, 2013 Edge Limited