Thanks for your answers Nick and Kryten!
Well ive considered it, but i would really prefer if i could stand up... And i really dont want to be forced to always have my neck crooked because there is 1 inch of height missing in the bus you know? And yes i've seen some videos where bubble foil was used, i just dont know if it would be enough insulation.. I know i can stand up in a school bus since i've spent all my highschool in one to get home, the only question is how will the insulation affect that.
By the way i am sorry if my english does not always make sense, im french so writting in english is sometimes a struggle..