I guess I can put this one to bed...
My Realtor (she rocks BTW) went out last Saturday with a tape measure and a camera and laid out where the tension cables are behind the 9' door part of the RV garage...and the results aren't good for wanting to drill to install a two post lift.
In this picture the black lines with arrows are the tension cables, purple lines are measurements from bottom and right walls.
I would want a two post lift with 108" (9') in between the posts which is the same width as the door. The cable on the left side of the door running up and down (North & South) is right in the way of where we'd have to drill.
To get around that I'd have to move the lift either too far to the left or too far to the right and neither is a good fix.
So it looks like we'll go with the commercial grade four post lift after all.
Here's a picture of the actual cables which are hopefully covered in concrete by now.