As mentioned, wind drag is a real factor with taller builds. It can add as much stress on the engine as weight. Really, once you get the weight in motion, initial acceleration, most smaller vehicles can easily keep weight in motion without a lot of trouble. Weight is a bigger factor in stopping, less so for towing. Wind drag though is a constant drag that can severely stress a little engine over time. So though the weight may be well within your vehicles listed range, wind drag could still cause real problems.
My TV actually has much worse aerodynamics than my trailer. The trailer itself, a folding design with lower roof line than the van, actually stabilizes the rig overall. My van is a lesson in what not to do aerodynamically.
