Think about air. Think about air flowing through a structure that is 50% stiffer than P 4/5 C's Ferrari GT2 based chassis, Front and rear subframes will be CF as well.
This is an issue in a lot of cars. Heavy duty batteries such as Extreme Odyssey can help but make sure you use their charger when car is resting as they require 14V. This will give fans the voltage they need at idle. Fan Shroud and exit ducting helps. If inlet can exit it's a disaster. Evans...
All Le Mans cars have high drag and low VMAX but... they do have downforce. With BOP a lot of GT cars do well. Look at the Astons. They lead the race for a long time and aren't very wedge like.
You no longer win Le Mans with VMAX especially with the two chicanes.
GTE Mustang and...