My 13í Scamp
never sways with passing semis. A slight tail waggle sometimes with a speeding tour bus- theyíre the worst- but not dangerous. We run about 12% tongue weight
with nothing heavy at the back.
17 is regarded as one of the more stable molded trailers, so I'm sure youíll be fine. If you want to add a friction sway control bar as an extra measure, thereís certainly no harm, and theyíre inexpensive. If you want to spend some money, Anderson makes a lightweight weight
distributing hitch that integrates sway control. Overkill in my opinion, but if you want the extra security itís an option.
Correct loading with adequate tongue weight
is the best sway prevention- the Casita 17 tends to run a little tongue heavy- along with keeping speed down and using trailer brakes