The hooks need to hold perhaps 2-4 pounds tops. Not much (That is total) you could use command adheasive hooks.
I used screws and eye bolts myself on my Damon Intruder (Fiberglass sides)
If you are worried, Do a search for studs.. Two ways.
One: Stud finder.. Or if you have a smart phone (I know it is out for android) Metal Detector app. Search for the nails.. NOTE: you will need to test to find the "Hot spot" on your phone.
2: On a day when dew forms.. Look at the side of the Trailer.. They stand out rather well.