My trailer thread has long gone adrift so here is the end of the story. Finally got a chance to take it out for a ride with the Roadster on it today. The Roadster got weighed months ago at 1942 lbs. Today the Dodge Ram, trailer and roadster came in at 9220 lbs. The Ram is supposed to weigh 5099 empty and had me and a bit of baggage on board so I estimate that to be 350 lbs. That leaves 1829 lbs for the trailer if I did the math right. Total weight towed is now 3771 lbs but maybe 500 or so is tongue weight. Tires are good for 4400 lbs and the axles are rated at 2000 or 2100 lbs each with torsion bar suspension. Trailer hub/drums, bearings, wheels, tires including spare and lights are all new as is the wiring and lights. Total cost to modify was about $ 2K Canuck or about $1530 USD and I have a trailer ready for two purposes.
I've had to deal with what is available to me for tie down strategy and for now we have crisscross front ( axle beam ) heading forward and rear end ( welded on loops onto front of trailing arm support ) heading aft with additional options for center forward and center aft if I chose to do so. I will add that on for the belt and suspenders approach noted by Al Gallow. I did add the two by fours inside each wheel as recommended by Danny. Wheel chocks are fitted up front.
I drove over smooth roads up to 65 mph, did a couple of swerves and very little action happened back there. Zero fishtailing but I never got passed by a tractor trailer either and there was no wind. The trailer brakes seemed smooth and effective. I went over a few rough paved and unpaved roads at 50 mph and stopped to check the straps and had to tighten a couple as Gordon predicted. The tires never moved on the trailer. Looks like Fla. here we come. I fitted a 3000 lb. winch on the front of the trailer and in the end it seems easier to just drive the car up onto the trailer. I sure like the back up camera for hitching up the trailer.... never had one before.
Still need to add inner fender wells on the trailer and rear mudflaps to the truck. The plan is to tow with the big bra on the front of the car and some type of plastic film on the windshield.