OK guys I have my new SMB penthouse w manual (human) lift. It is a big son of a gun on an extended Chev. Pushes up a little harder then the short wheel base sample we tested at SMB-I. Soooooooooooooo I got thinking. My penthouse top is say ..... 50" wide by about 120" long.....that translates into about 6,000 square inches of surface area. So I close the doors tight, set my vehicle ventilation system to outside air and set the blower to high. The sides of the raised penthouse bulge out! Not sure what it takes to manually (human...me) lift the penthouse roof ... maybe 50-75 lbls?? Well with 6,000 square inches of roof area all I need is to pressurize the inside of the van to 0.01 to 0.02 psi and the roof will go up. If not by itself at least a lot easier. Guess what, IT DOES GO UP EASIER!! So the heck with opening the doors before raising the roof. I am going to leave the engine running, close everything up, set the blower to outside air and turn it on high. Then raise the roof.
Those w manual roofs .... try it both ways.