After last week end with 2 - 18' kayaks car topped and running into a 70 knot squall I need to rethink my tie downs for car topping. Other than rope and knots I'm looking for alternate tie down options. Crank straps from HD seem to work but the large metal crank worries me being next to the kayaks. Could be a possibility for damage while going 70 MPH.

Too much mechanical advantage on the end tie-downs can easily damage your boat, before you ever hit the road. I'd be careful.

I got some strap(webbing) end-ties in a deal for a roof rack, but only used them a couple of times. They really do 'get in the way' visually and no matter how they are twisted, they vibrate at speed. I went back to 1/4" line and trucker's hitches. I installed some stainless straps and carabiners at the ends of the car, and that speeded up the attachments.

Once you know how to tie knots, and have lines of the right length, it's only a matter of a few minutes to tie the boat ends. (Two lines per boat, per end)