Hello Roger.
I have looked into the issue of the ground level of the bleachers in more detail. I have been using a very specific programme to evaluate ground elevations. For me it is an exceptional program and appears to give very accurate data. The website is called: randymajors.org
It allows you to mark lines on the ground for detailed ground profiles, and also allows you to download an Excel spreadsheet of the data points themselves.
I enclose along with this message a screenshot detailing my evaluation of the bleachers.
The blue rectangle is the precise mapping as near as I could get it for the exact perimeter of the bleachers in terms of position and orientation. The program itself mapped the ground elevations along the perimeter line, as shown in blue.
I marked the corners of the rectangle as A, B, C, and D. The program generating a graph for the entire perimeter, which is at the bottom of the screen. I further added the corner point letters next to the graph also, indicating their various ground levels with a black blob.
The results were quite fascinating. It would appear that there is a rather sudden change in gradient of about 1 foot cutting through the bleachers position. The very front of the bleachers are positioned on a very level piece of ground that is about 1335.6 ft above sea level.
Almost one full side of the bleachers (A-B), and all of the back of the bleachers, are at a level about 1 foot less than this. Interestingly enough, the position of the wheels near the back of the bleachers are in the middle of this low position.
If you look to the data points to the right of the image, you will see that the wheels have a ground elevation of some 1334.72 ft.
You have stated that it is best to use the wheels as the key point of reference for the ground elevation that we are seeking, and I see the rationale behind this.
As a result of this, I believe the correct value above sea level for the ground height that the bleachers rest upon should be this value: 1334.72 ft. Of course this certainly does differ from the value that you propose, of 1336.32 ft.