Just some additional thoughts
First, my condolences to the pilot's family and friends as well as the family and friends of those who were lost in this very tragic accident. I will continue to pray for their loss and for those recovering from the accident.
This site has some remarkably clear images of the trim tab (or lack thereof), as well as the airframe. I suspect that during the race, the pilot likely had a lot of down trim dialed in to assist him in keeping the nose from rising at the speeds they were at. If this was the case, and it may not be depending on the actual way the aircraft was "rigged" for flight, when the tab departed, the loss of down trim would have created a rapid and violent pitch up. At race speeds, the G- Forces would have been spectacular. For the sake of discussion, let's say the G forces caused the pilot to blackout and at that point the plane was in control.
(as a note, during my flight training my flight instructor who was a lanky 6'5" ish guy was able to get his foot in a position to put pressure on the yoke without me seeing him do it. As the stick got "heavier" I dialed in some down trim, then more down trim, and more until I had run out of trim and was pulling on the yolk with many pounds of force. He then slipped his foot out, and the plane shot skyward very abruptly, which startled the crap out of me, and also required a huge amount of force to overcome. This was done in a Cessna 150 at maybe 90 knots, not ~500Kts.)
Since only one of the trim tabs departed, that could cause a asymmetric amount of lift on the elevator which could have cause the slow roll that was caught on video. I have heard the aircraft performed "lomcevak", but, I personally didn't see that in the video. I have also heard that the aircraft "snap rolled", but again, that's a violent roll, and the roll was slow, not the quick variety a snap roll is.
So we have a violent pitch up which appeared to produce an "L" shaped loop as they call it in aerobatics. The L loop is produced when the pilot holds the stick aft over the top of the loop, which pinches the top of the loop in to an "L" shape (think of a cursive written lower case "l"). While this loop is being executed, the plane is also rolling slowly. This is what I observed in the videos I have been able to watch.
As the aircraft started on the downside of the loop, it was clear the nose tried to flatten out which some have suggested might have been caused by the pilot trying to avoid the crowd, which I believe he would have done if he was able. It also appeared the roll ended on the bottom side of the loop which could indicate the pilot was beginning to resume control. He may have pulled hard at the end of the flight to try and avoid the grandstands, and that may have just put the plane into an accelerated stall into the ground. This is my theory, and I am not an expert.
Having had the pleasure to meet many of the pilots who race, I firmly believe that the pilot did everything in his power to prevent the loss of life, and that he's horrified that so many perished.
Thank you for letting me post here, your site seems to be the most objective site I have found on the web.
Also, one last note, the emergency response was incredible. I know they prepare for just this kind of accident, and the crews were on scene quickly, professionally and no doubt saved who could be saved.
Rick