-- Last Updated: Apr-22-13 2:59 PM EST --
I am not sure where you got the both pull in or both pull out thing from - I haven't heard it be a reason not to use them. It is simply not possible to do that on most cars anyway, and having imperfect lines is a better idea than not having them at all. Bow lines especially, because they tell you if a boat is coming loose before it has gone flying off the roof.
We have loops coming up from the bumper guards and tie off to that on each car. We have used bow lines with long boats as well as my Innazone 122 - a boat that is surely shorter than any rec boats you are carrying. The boat is a tea cup.
Stern lines are more problematical for us - we don't have something easy like a trailer hitch in back. After ourselves and others nearly having flapping stern lines wrap around a wheel well and leave half of a snapped off boat on the highway, we don't use them on the kayaks. For a long trip we double up the regular straps, something which came to us from one of the gods of kayaking in the US so we presume it is a good idea. I do add lines in back for the canoe because it is such a wind sail, but the canoe doesn't get carried across states like the kayaks. The stern arrangement for the canoe probably faces the wrong way against what you were told. It doesn't matter, and it hasn't failed me regardless of it tucking in or out.
Later add re the directional thing - if you wanted you could always run a line from each side up front, put a loop in the middle to establish the top of the triangle, then tie off the bow lines from the boats to that. I am not sure this is a winner for two reasons - as any climber will tell you, more knots actually weakens a line. And it could reduce the information you are getting that will allow to to easily tell if a boat is loosening up on the roof. But it would be possible to do this.
Hardshell Kayak Sail Rigs
Pull-Up Strap Handle Kit
|Table of Contents|