I might consider an inadequate tow vehicle for a short, less than 10 mile run on flat roads but not for 1000+ mile trips. If the trailer weighs more than the vehicle, the trailer will be in control if things go awry. I saw a video of an SUV towing a not particularly large trailer - the trailer blew out a tire, started skidding around sideways and ended up flipping the SUV. I've towed lots of boats on trailers (including a 36 foot catamaran) and it is a MUCH more relaxing ride when the tow vehicle is over-built for the situation.