I would get the base plate installed on your PT Cruiser and do some measuring on it and the RV before you decide what drop receiver to use. Sometimes, the measurements they give on the height can be a bit off from reality. :)
Also understand, contrary to what some say, it does NOT have to be perfectly level. As long as you come close, you'll be fine. I would agree that you'd never want the RV end lower than the car end, but it is OK if RV is a little higher.
Also keep in mind, there is a huge downside to using larger drop receivers. The more the drop and the longer your MH's rear overhang is, the more likely you are to s****e or drag the back of your MH when going in and out of driveways, gas stations, etc. Too much 'drop' can put you at so much risk for tearing up your reciever or tow bar, you're better off to live with the tow bar not being quite as level.
With ours, I use a 4" drop, and it is not level (MH is maybe 1-2" higher). However, there is NO WAY I will use any lower of a drop. I already s****e a little when backing into our driveway and other places. if I went any lower, I'd probably tear the hitch receiver or tow bar clean off (or get it stuck).
