I just want to point out that the car has a serious design failure of placing the ESC like this, your motive to move the ESC backwards is good but doesn't help a lot.
Besides, you have to consider if the support plate u make is broken. Your ESC will touch the rotating rear centre shaft which is made of metal. I think it is very dangerous that the wires may jam into the rear shaft.
1) Sell this car and change to other ones
2) Cut away the receiver box and place the ESC there, then put the receiver somewhere else as it should be small; or u can even put the receiver on the centre gear box with proper protection.
3) Make a stand similar to the ones that ching has made, but with better material like alloy, lower position, and preferably with supporting "legs" to the chassis, OR you can even fix the custom made ESC stand to the rear chassis brace.