I talked to Lonnie and he said he did not think it was a cooling issue. I have plenty of breathing room above, behind, and below, so that should not be an issue. He did say I could move one mono over to the next slot to create a little more breathing room within the chassis if I want.
After talking to Lonnie, I'm pretty confident that I was just pushing the amp to its protective mode. Since it came right back on he was sure there was no problem with the amp, it was just the circuitry portecting the amp. He said he could tell me how to turn that off, but he would not recommend it.
If you keep in mind that my measurements were being taken from the seated position, about 13 ft away, and I was getting peaks up to around 106-108dB's. If I move closer to the source by half the distance, 6.5ft away, that gives you and increase of 6dB or 112-114dB, then again cutting this by half to get closer to the one meter (3ft) range, your talking 3 ft with 118-120dB's. In reality, I'm sure I was hitting higher peaks, just not watching the SPL meter closely.
Based on my 95dB 4ohm Axioms, 120dB's would be pushing the 300Watt limit of the amp, so I guess it makes sense that it would shut down.