About the length: I occasionally tow my kayak with a trailer. My bike, trailer and kayak have a combined length of over 7 meters. Sure, it can be awkward, but mostly because the kayak exceeds the trailer's wheels by a good 2 meters in the back. You will not have that problem. I don't think the length itself is a big issue. You do have to be aware of it at all times, especially in curves and junctions, but that awareness develops quickly.

--J