See thread below for my journey through the same dilemma. Had a Jayco Rep actually send me some information out of a Powerpoint with photos on how they build the fiberglass sides for the JayFlights… in the end I decided to go with Aluminum and have been very happy so far.
They are not Vacuum Bonded over an Aluminum Frame like the JayFeathers (I had one previously). The fiberglass is pinched rolled with glue to a thin piece of luan then Glued to the wood studs.
As you will see in my thread there are a lot of views on this subject and they are all good and I appreciated all the feedback from everyone.
If you are interested in the Info I was sent, PM me and I can send it to you.
JayFlight Fiberglass Sides