Food for thought...
Having car topped a Hobie Outback on my Subaru Outback where the roof rack is not as high off the ground as your 2001 Xterra and have "experienced car top loading issues", I can offer one bit of cautionary importance.
If it's the least bit windy, you need two people to load a PA-14 as it can quickly "get away from you" while loading.
Not only is the PA-14 heavy and 14' long, but it's wide and "makes a wonderful sail" in the wind.
I have owned a PA-14 for the last two years and use a Hobie Trailex trailer modified with 3" Schedule 40 PVC parallel pipes.....From your post, saving money at this time is important, so looking for a used PWC/Jet Ski trailer is one good option as they are generally less than $500 for a single wide trailer and easy to modify.
Using a trailer for a PA-14 is not only safer but it's ready to go fishing on a moments notice.....