Well....... someone thinks it's a good idea.
If you want to try it, I
wouldn't make it sound like it's gonna fail and no warranty because you're afraid to, or you'll come across as being a nutjob for charging so high for something you know is gonna fail.
Do your homework, make sure you can give him his money's worth and explain to him due to the level of difficulty in doing this job correctly and using the best materials at your disposal, you need to get
$XX.xx to do the job. Explain that your concerns with these trucks are all the little nooks and crannies and you'll need to take some poetic license to change your normal way of delivering this project to give him the best job for his money......
OR you could do partial wraps of selected strategic areas and do it for
$XX.xx amount.
Whatever you do, don't burn any bridges.... just get paid well for your job.