Scooter,
Take it from a long time sea kayaker with 18' kayaks. Spread those racks as far as you can,and use bow & stern end tie downs. Even at that length a passing truck will wind buffet your boat to pieces. The narrow rack spread will allow the boat to piviot,and put undue stress in that area. Bow & stern lines will help prevent what us sea kayakers call rack whip. The piroque is the same as a canoe,air will get underneath,and try to lift it off the racks,again bow & stern tie downs will help prevent stress at the rack points,or rack release from wind pressure. Since your boat is not reinforced inside by bulk heads it is more at risk of damage from rack whip. Many boaters fail to use bow & stern lines,and end up sending their boat into the windshield of the guy behind them. I can't see if your rack is factory,or aftermarket,but canoe gunnel stops mounted on the rack also helps with rack whip. If the Element has no place underneath to tie the tie downs to,there is an easy fix that works on almost any car. Take some flat nylon web strapping,and fender washers. Open the hood,and look for fender bolts along the hood edge line. Remove the bolt,make a loop in the strap,drill a hole in the strap ends. Take the strap run the removed fender bolt though them with the fender washer on top of the straps,and bolt to the fender. Make them long enough to allow the strap to be outside the vehicle when the hood is closed. When not in use ,open the hood,and fold them inside.{see picture link} For the stern lines you can usually find plenty of places to make a heavy nylon rope loop to tie the stern lines to. Need more info PM me. Just hate to see you loose the pretty boat before you get to enjoy it
http://outdoors.webshots.com/photo/2525 ... 6027QsongZ
old setup,and vehicle,but with my sea kayak
http://outdoors.webshots.com/photo/1143 ... 6027lQDlhG
In the first picture you can see the bow lines and my nylon tiedown loops,at the rear I just tie to the trailer hitch for the stern lines.
pateardropper