I bought the Stacker so when my wife bought her kayak we would have a way to transport both her's and mine with my very small, 2009 Toyota Corolla. I'm affraid to say that I may have made the wrong purchase. Here is why.
I transported a friend's kayak along with my own this weekend. This was no trip down the street but a 300 mile trip to the beach from eastern WV. I was not very sure about the whole system. The tall bar that stick up are easily moved around and bent (they spring back) with no weight on them. The straps were very poor. After a test drive I switched the supplied straps for a set of light duty wratchet straps. This held the kayaks firmly in place, but put the verticle bars on a lot of strain. The whole way to the beach I could do no more than 65mph. Anything over would make the boats bounce and shift. I did NOT want to make the evening news.
While loading the boats back onto the rack for the trip home, I removed the Stacker, and we sat both boats side-by-side with the hulls down. They juuuuust fit.
So in all, I think I may return the Stacker and exchange it and purchase a second hull saddle style mount or something of that nature being that I am only ever going to be transporting 2 kayaks.
At the end of the day, the Stacker got both boats 300 miles safely, albeit shakey and scary at times.
I think the Stacker would benefit someone with more knowledge on how to properly use one (the instructions explain very little differently from how I used to) and/or someone who has limited space and must transport more than 2 kayaks.