We need some engineer to do the calcs on this, to see how much pressure I was creating by blowing the pad up as much as possible, then standing on it with the 2X6 board with my 160 lbs. The board in question is 21.5 inches long, just as wide as the pad. I need to see now if I can repair it, wasn't thinking along those lines last night or this morning. I don't even think a repair kit is available for it yet. I will email Customer Service at Cascade Designs, as Sales has no clue what a NeoAir is. I thought that was hilarious when I emailed Sales and they went huh?
I just couldn't stop myself from applying some forensic structural engineering to this product failure. Based on physics, you didn't add any significant "extra" pressure to the mattress by distributing your weight on a 2x6. Because the chambers are all connected, the pressure inside the mattress would be the same if you laid on your back or your side on the mattress or used a board to distribute your weight. There could be a slight delay in balancing the pressure if the air movement is constricted between the chambers, but eventually it will be about the same no matter how you apply your weight. Try squeezing a balloon in your hands and you'll see it doesn't matter how you squeeze it as long as the force (your weight) is the same.
There are a couple of unusual conditions that could occur. If you "bottomed out", then some of the load would be carried by the ground and the net pressure increase would actually be less. If you applied the load very rapidly, then the pressure might not balance between the chambers quick enough in which case you would see a temporary spike in pressure. You didn't mention jumping on the board so lets rule that out. The take-away point is that the mattress did not fail because it had too much pressure. It did not explode.
However, there is an important difference between laying directly on the mattress and putting your weight on a 2x6. The edges of the 2x6 will cause local shear stress concentrations to the mattress fabric that you wouldn't get by distributing the load more evenly (i.e. laying on it). Having the mattress fully inflated would increase these local stress concentrations, as would any movement of the 2x6 or the mattress. You mentioned lifting the mattress to see the under side while standing on the board. The fabric shear stress concentrations are probably what caused the 3/8" v-shaped tearing damage you describe. I suspect that the tear occurred near a corner of the 2x6 as you were lifting the mattress.
These mattresses probably have a good safety margin built in against explosion, with the seams being the weak link. Its the fabric tearing or puncture that you need to protect against. Having written that, a fully inflated and heavily weighted mattress will be more prone to tearing or puncture.
I'm glad they replaced your NeoAir. I think I'll stay with my Prolite3 or 4 until I hear some long term success with this one. Saving the ounces is tempting though...