@fidalgophil Thanks for reaching out!
For transporting a kayak on the roof of your car, it's hard to beat a 'J'-Style rack like the Yakima JayHook Kayak Rack or the Thule Hull-A-Port Kayak Carrier. They are secure, durable, and easy to use. If you don't want to have the racks sticking up when you're driving without the kayaks on, we suggest looking at the Thule Hull-A-Port Aero Kayak Rack or the Yakima BowDown Kayak Rack. Both of those racks fold down when not in use for a lower profile. You should have no issues fitting both your kayaks on the roof of your car with these style racks.
Hopefully that helps, let us know if you have any other questions!
Everything @REI-JohnJ said is spot on from my experience cartopping. I just wanted to add that as I obtained larger kayaks such as my Jackson and Hobie I found cartopping to be too much at a certain point and I eventually went to a Yakima Rack and Roll trailer and truly found this to be a game changer. Not trying to sway you in any particular direction. If I continued to just use a couple smaller and lighter kayaks the JayHooks would work great