What's the tow rating of the VW? How much does your Speedster weigh?
I flat-towed my 1500 pound Spyder with my 3300 pound Legacy GT with 165hp. It worked, but wasn't very much fun on hills- downshifts to 4th happened often to Carlisle. My V6 Passat was much better with 195hp but more TORQUE. Better than that was the V8 Audi with 300hp and HUGE brakes for flat towing.
Best yet though was my dedicated single-axle car trailer with brakes at 700 pounds. Ultra light and effective, towing 2200 pounds with a 3500 tow rating was great. The mileage didn't even go down much at all with this rig.