Not the problem I was expecting to have

If you want a stressful tow continue using the navigator. The Navigator will make a marginal TV at best. It has a soft suspension, poor gearing (for towing) and not really enough power. Sure you can floor it and let it rev to get a bit more power out of it. But is that really how you want to travel?
There are better more relaxing options.

At this point your observations are correct use the Navigator for now but if you plan to tow the trailer regularly you will need a more capable TV.