Here's the deal: I have a 2005 built 24' Winnebago Class C. Over the last few years, I've towed both my old Z06 and RX8 on open trailers, which I figure is probably in the 4900-5100lbs range. Tongue weight I would estimate in the 500-600 range. Now, I'm looking at towing my Mustang, which adds about 300-400lbs to the equation.
I know I've been exceeding the manufacturer's reccomendations on tongue weight, as the Class III hitch on the RV (although rated at 500lbs like all class III's) is limited to 350lbs tongue weight per Winnebago. So far, I've had zero problem, including tows to Topeka, Packwood, San Diego etc. It tows great and I've visually inspected all the hitch's mounting fasteners and the frame extension welds many times, with no concerns. btw, the frame extension is not super long (as the RV is only 24') and is spliced using the Ford reccomended procedure, which is kind of a sleeve with triangulated extensions welded at multiple points to both the original frame and the extension piece.
Anyhow, I'm feeling the Mustang may be putting close to the brink in terms of the current set ups safe capacity...not in terms of total weight (my theoretical GVWR ceiling allows about 6300lbs), but more in terms of the Class III hitch and the frame extension. So, the questions that I'm hoping some might have thoughts or, better yet, experience with:
1. How do these RV manufacturer's arrive at the max towing ratings?
2. Has anyone beefed up the frame extensions on a Winnebago or other Class C?
3. Does it make sense to weld in a Class IV and go to a weight distributing hitch, at this point? (Given I have no sway or other issues, but the front is getting a little light and I'd also lower the weight load on the rear axle, which might be getting closer to max)
If anyone has any solutions/ideas, I'm all ears.