kayak rack

Hello, I tried looking online at cross bars but I noticed most manufacturers do not post the height of crossbars above the top so I am hoping someone with crossbars can answer. I need a crossbar to match up to the crossbars on my topper which is 3”. Anybody have any crossbars that are that...

Wanted to post a quick pic of my current solution for a canoe/kayak rack: Rear rack is one of the pair from this set: https://www.amazon.com/gp/product/B07H2XQMFH It's held down with these clamps from the same company, but I'm guessing most any rack clamps would work...