[Mikendebbie]

Montana Man said - It appears that most of this cracking is due to keystone's lack of basic engineering. I wouldn't blame lippert for this one. Designing a square cornered opening near a flexing point is about as ignorant as one can get. What I don't understand is their ongoing use of this design. Until you follow the money and find the answer. Keystone, I dare you to chime in and shed some insight to this matter.

I agree. Look at my illustration below. Units that have a slide-out located forward where my red lines show have very little structure under them at the flex point (pink area). The slide in my unit is located much farther back and is surrounded by a bit more "meat" in the structure. This is pure speculation on my part. I'm sure there are ways they could engineer the pink flex point to provide more rigidity and strength...but apparently they have not followed that path.