Carrying Kayaks on roof (does antenna come off roof?)

[Canoehead]

Also will 1 ratchet strap in the front window, 1 ratchet strap in the rear window and a rope tying the front of the kayak down to the eye hook on the front bumper be enough?

ie: No rope needed on the rear?

I much prefer the front tie-downs to provide both lateral and vertical support - meaning pop the hood, tie webbing loops, then close the hood with the loop sticking out. A long boat will want to twist sideways in gusts, so two bits of parachute cord holding it from side-to-side really helps.

I have taken canoes on car tops for thousands and thousands of miles. One line on the front and none on the back will probably work, but given the consequences of failure (possible death to the person behind), I don't risk it. I put a minimum of 2 lines on the front, cam straps or rope to hold to the roof rack, and one rope on the back.