Store paint flakes off. Polycarbonate paint sticks and is flexable whereas store paint lacks flexability. It will work in the beginning, but with time it will flake off.
Being on the inside, those paint flakes will probably land on your chassis.
If it was a crawler body and on the outside I...
You want Tamiya "PS" line. Thats for polycarbonate.
The TS is for hard plastics.
https://www.google.com/search?q=tamiya+ps+paint+chart&client=ms-android-att-us&source=android-browser&prmd=sivn&source=lnms&tbm=isch&sa=X&ved=2ahUKEwinwua8gZn5AhUVZTABHZrrB_UQ_AUoAnoECAIQAg&biw=360&bih=520&dpr=3
Hold it up to light or the sun, lookong through the body. If I see light, I shoot.
Look for bright spots, clear spots, and splatters in corners that dont cover the entire area.