Just for the sake of comparison-- I just purchased = the Thule Rack with the bolt on rain gutter sections that mount to the = fiberglass top.  I happen to carry surfboards (4 at time now with = the new rack) and just got back from a San Francisco to San Diego trek = this weekend.  Thule has an excellent canoe/kayak holder that = would add on to my installation and would not be significantly heavier = than the 4 surfboards. 

I have had no difficulty with the application-- I = drilled the holes, sealed with 3M 5200 (bullet proof) and am able to = pop the top and open the vent with surfboards (not sure about the = wisdom of doing this with a canoe) attached.

Could definitely take some digital pics if anyone = wanted more details.