I honestly don't think it will be very tall. The latest concept art (which I take to be more "true to scale" than what was shown at D23). It appears that the "peak" of the mountain will actually be built on top of (and to partially hide) the main show building). shows cars driving up that mountain and that tallest point only being maybe 10-20 feet above the cars.
I tried to make some sense of the image. Based on what I can see, it seems the ride will be as follows:
1.
Entrance/(Exit)?: I can't tell if this is the formal ride entrance or just the entrance of the show building. Either way, you may either walk (or drive) past McQueen and Mater as you enter the main show building. Or maybe it's possible that this is the end of the ride and you go past McQueen and Mater before making a left turn to the finish line (H)[which I have no other way of getting to otherwise)
A. Show Building Race Exit: It looks like you will have a dark ride portion (similar to RSR) prior to exiting the show building to start the "race"
B. Start Line: You can see the start line here indicating the start of the race before the cars make a180 degree turn to the right before going over the bridge
C. The Bridge: Shown in a lot of the concept art
D. Under the Bridge: After the bridge the cars turn 270 degrees to the left to go under the bridge they just crossed
E. Tunnel/Cave: After going under the bridge, the cars turn 180 degrees to the right again to go through a tunnel/cave (that goes under the path the cars previously took before going over the bridge)
F. Mountain Ascent: After exiting the cave, there is a (mostly) straight section where I assume the gyser/mud aspect will come into play before the ascent up the mountain
G. Mountain Peak: At the peak of the mountain, the cars will go around the signature mountain peak before making a turn and going... well, who knows!
H. Finish Line: Eventually, you get back up to the finish line, but I can't see where there is an outdoor path here or if maybe the ride goes back indoors for a portion before making it to the finish line.
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