If the 17' Casita
in question has no bathroom up front, it could be ok. The front bath is what makes the 17'er so tongue heavy. Like Dave pointed out, a 16' won't have that problem.
I'm assuming your Santa Fe has a maximum tow capacity of 3000 lb but I could be wrong; what does your owner's manual say? A dealer could run your vin
number and tell you if it's equipped with tow package, and if not, what should be added to your vehicle to make it ready for towing. Sometimes an aftermarket transmission cooler is needed, for example.