I don’t have enough knowledge on the subject to suggest a solution.
But asking a question along a tangent since you mentioned heat:
Which colour does your van and its roof/interior have?
If its a darker colour, maybe trying a lighter colour would help reduce the heat gain?
https://www.youtube.com/watch?v=W_2lsMXR_wo
https://www.youtube.com/watch?v=qLVNjS403M8
Only the living have a problem with anything tho