After I get the camera leveled and pretty much set up, I put the elastic portion over the back standard only. However, I do not let the hood touch the bellows. You have to look carefully at the configuration of your specific camera to determine the best place to affix the hood given the specific shot you are taking. Sometimes I end up sticking a cloth under the space between the bed and the back standard for another form of a light seal when I need to really check critical focus. There is a lot of surface area to check on 8 x 10.

Having used a one dimensional flat cloth hood over the camera, using the lightweight hood from DI is a breath of fresh air. Try several configurations to find out what works for you.