They work great for carrying 2 kayaks on a vehicle, but it is hard work getting even a 45 lb. kayak up on these j-hooks, on top of a small SUV. We have almost had the kayaks fall off while loading. Also, racks are very noisy when no kayak is strapped in.
I would opt for a lower profile kayak rack if I only needed to carry one kayak.
I've been using Thule racks on my cars and trucks since the mid-1980's. My kayak saddles (from 1987) have worked well, but I thought I would try out the Hull-a-Port. I wish I hadn't.
They are made to universally fit all bar shapes, which means they do not firmly lock on to the regular square Thule bar profile. When you try to reposition a heavy boat they tend to rotate on the bars. In addition, they are super tall so even my little Audi wagon has trouble fitting in an average parking garage. Gas mileage also takes a big hit. I ended up taking them off and threw them in the corner of my garage and went back to my 20 year old saddles. This is the first piece of Thule gear that I have been disappointed in.
The new version that folds should be better. I may give those a try...