Hiya, Jack....nice to see you back up and online with us. I've had mucho experience towing cars...towed my '85 911 Carrera all over the southeastern part of the US for over 12 years. I now own a 20' Pace Shadow that I tow my SPF in.
Like most others, I do indeed endorse a weight distributing hitch. This spreads the weight more evenly across all axles on the trailer and tow vehicle, and keeps the rear of your tow vehicle more level when you hook up to the trailer. Also, if your combined trailer and replica weight exceeds 5k lbs, an anti-sway device is a very good suggestion. You'll be amazed at the difference once these two improvements are made!
But, there is also one thing that has been eluded to by Cobralee in his post above...you MUST have at least 10% of the total weight of the trailer and load on the hitch tongue! Failure to do so
WILL cause the swaying you experienced, especially at high speeds -
TRUST ME ON THIS!. Since you and I both have a lot of aviation experience, you'll understand this swaying is sorta like a 'dutch roll' induced by too much speed and too small a verticle stabilizer surface. I have experienced BOTH the dutch roll and swaying trailer syndromes, and I can tell you the trailer is a much more nerve wracking experience!
Take your trailer with your Cobra in it down to a reputable trailer speciality shop. Tell them you want them to set your 'tongue weight' to balance your load with the Cobra in the trailer. They'll have you disconnect the trailer/Cobra from your tow vehicle and then they'll use a small scale to measure the weight on the hitch tongue. They'll probable ask you how much your Cobra weighs, too, so be prepared. Then, they'll most likely have you move the Cobra either forward or backward in the trailer to get 10-12% of that total weight on the hitch tongue. I'd suggest you taking both cars down there in separate trips so you'll know exactly where to position both vehicles inside your trailer.
Now, once that's done, should you decide to move other 'stuff' with your properly balanced trailer, simply start loading from the front of the trailer first. You want to make sure the bulk of the weight is in the front of the trailer. Preferrably this should be 10-12% of the total weight, as I mentioned earlier, but this will be difficult to calculate since you won't always have the weight of your load handy. For those occasions, I'd limit my speed to 60-65 tops...if you start swaying, however, your anti-sway bar and weight distributing hitch should control most of that much easier.
I damn near lost my Porsche on it's open trailer outside of Nashville several years ago because I had allowed my car to roll back several inches from the point that had been marked on the trailer. This caused the tongue weight to become too light for the load. It towed just fine until I got over 65. When it started to sway, the ice in my cooler in the back of my Explorer was sloshing back and forth so much that it splashed out of the cooler! That damned trailer was pushing me from one side of the road to the other and all I could do was try to keep the steering wheel centered and keep all the wheels going in the same direction. I just took my foot off the throttle and allowed the truck to slow down on it's own. Once I got below 55, it stopped swaying. I immediately knew the problem was the tongue didn't have enough weight on it. Sure enough, when I stopped at the next rest stop, I found the car had not been all the way against the chock when I strapped it down. I loosened the straps, moved the Porsche forward, and re-tied it down. Towed fine after that all the way back to Memphis.
MORAL: Weight distributing hitch if your combined trailer and payloiad exceed 5k lbs, anti-sway device for trailers 20' and over, and 10-12% of the total trailer and payload weight on the tongue. It'll tow just fine...
Hope this helps!
