So....I've been pondering this question for some time: should I carry our two kayaks on the TC roof or get a small purpose-built kayak trailer? Both solutions have pros and cons. I like the idea ...
I'd try out the roof mounts since you already have them. Actually, I'd check the weight capacity of the roof and try to figure out how hard it would be to raise the roof with them onboard.
We carry a 19' canoe on our popup--if we had a trailer that long we might as well haul a travel trailer and get some elbow room. It's light enough to pop up without removing the boat. I think kayaks are in trailer territory.