Here is a video of the 2011 Reno crash, thankfully not taken to impact. You can see Jimmy hit the wake turbulence as he rolls downward in pylon #7. He had modified "The Galloping Ghost" trim system so the entire trim load was taken by the port trim tab, with starboard trim tab being fixed in place. It was never designed for the entire trim load ...
View: https://www.youtube.com/watch?v=xoncG_j5AdI
In this video you can see 2/3 of the port (inside) trim tab depart the aircraft in the pylon #7 turn.
The P-51 is heavily trim sensitive and immediately pulled up with 16 - 18 g, knocking Jimmy out for the duration of the flight.
Blue skies, Jimmy.
If you Google the 2011 Reno race, you can see the result, but the impact is NOT what I was presenting. Rather it was the reason for the impact, which is the trim system modification that was never tested at 500+ mph in race conditions at full power. That won't happen in the future. You can modify the wings and tail, but NOT the trim system without demonstration via full flight test at race speeds including wake turbulence.
So it will be expensive to make a departure from the accepted flight systems of the certified aircraft in the trim system.
Of course, if you make an original aircraft, you must submit full fight test data at race speeds to be accepted for the race. If you BEAT those speeds by much (a few percent or so), then you may be disqulaified for sandbagging the test results.
This may happen again, but shouldn't with the steps taken to make sure the modifications work at race speeds barring structural failure.