After looking in the attached 1977 Owner's Manual, it reads like the Raising/Lowering switch is in basically the same location that is is in our 1970 Hi-Lo.
In our rig, adjacent the door, on the end side of the goucho couch, we have a little cabinet door (5" X 5"). Inside is a spring loaded toggle switch... up to raise, down to lower, springs back to the middle position when done. A finger loop for the hydraulic ram safety bar release cable comes up through the floor just below the switch. Assuming the bar is operating properly, you will not be able to lower the roof half without first pulling the cable to release the safety bar.
If not the same as the above description, please let us know how and where yours is different.
1967 17' Hi-Lo Bon Voyage (1967-1969)
1969 19' Hi-Lo Bon Voyage (1969-2011)
2004 27' Hi-Lo TowLite (2010-present)
2015 Chevy Tahoe LTZ