Not sure how much the vin will help you with the model number... as an example, using this decoder, it tells me that I have a 5th wheel and that it is a Rockwood Lite Weight Trailer... My actual model is not decoded and I know that Rockwood makes more than one light weight model...
ftp://safercar.gov/MfrMail/01-22-N11B-7432.pdf
How about the labels on the camper, there should be a yellow (weight) and a white (tire info) usually on the outside, lower left corner (Driver's side) of the camper. My white label includes the model number in the information. I also found the same labels inside the camper, low on the inside of the door...
A phone call to Forest River might be your best bet!
Good luck!