Ed/Jason - I did some research on the weights of the 19RR with different siding and I stand corrected. Ed was right with the FR 19RR, going fiberglass with the siding adds approximately 500 lbs based on what the dealer said.
FR did not post the weight difference on their website, so I asked the dealer I bought mine from. He said with FR, they do not change the overall construction of the trailer when you go fiberglass. They still have the same paneling on the inside, then a frame structure and then just the outer skin can be aluminum or fiberglass.
The dealer said the "ultra light" trailers that you see and are typically fiberglass (smooth) use a totally different construction where the entire wall of the trailer is much like the doors on the 19RR, with two thin layers of skin laminated to a solid Styrofoam core. This laminated wall construction is strong, thin and light, but the dealer said very hard to repair without the internal frame that is more typical and like the 19RR has.
I stand corrected that the aluminum sided 19RR is the lighter of the two.
P.S. - Jason -I will go out an remeasure from the rear gate to the rear of the fender well and get you the width of the fender well and the distance between the fender well and cabinets. I will send those to you in a private message, so I don't fill up this forum with dimensions. If anyone else wants those dimensions, let me know and I will forward the messages I send Jason.
2012 Grey Wolf 19RR
2012 Toyota Tundra Crewmax 5.7l
2006 Road Star Warrior