Been towing open Trailex with GL450 or GL350 Bluetech for 2 years, about 50 events, with no issues. I use cruise all the time with transmission in normal drive position. The 350 Bluetech is great for towing this load, with its low end torque you almost don't notice the tow.
Bob
2012 Interseries Cayman S #17
2006 997 GT3 Cup #18
2012 Interseries Cayman S #17
2006 997 GT3 Cup #18