I am getting a CoverCradle lifter for my new Vanguard. I'm not sure if they're giving me the CoverCradle I or II (is there a big difference?). I noticed that on the specs it is suggesting that you have a 24" clearance in the back. I have some ficus trees directly behind the spa I don't think that I have more than 20 inches clearance. Would 20" be enough for the back? Is there a work-around for making it a little "tighter" if needed? If not, would a side installation work? Any downsides to doing it that way?